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Fuel Efficiency and Slow Driving?
vile8 writes "With the high gas prices and ongoing gas gouging in my hometown many people are trying to find a reasonable way to save gas. One of the things I've noticed is people driving exceptionally slow, 30mph in 45mph zones, etc. So I had to take a quick look and find out if driving slow is helpful in getting better mileage. I know horsepower increases substantially with wind resistance, but with charts like this one from truckandbarter.com it appears mileage is actually about the same between 27mph and 58mph or so. So I'm curious what all the drivers out there with the cool efficiency computers are getting ... of specific interest would be the hemis with MDS; how do those do with the cylinder shutoff mode at different speeds?" Related: are there any practical hypermiling techniques that you've found for people not ready to purchase a new car, nor give up driving generally?
I spent some time researching this matter after a discussion at work started about it.
Something that I had observed in my car was that my fuel economy increased as my speed increased.
At a cruising speed of 85mph, I get 26mpg. at 80mph, I got 24mpg. And at 65, i got about 20mpg. This testing was done along I-10 between Jacksonville and Los Angeles. There's lots of room to set the cruise control. A test usually consisted of fueling up, then a hard acceleration to the testing speed and setting the cruise control to handle maintaining the speed for the next 300 to 350 miles. Individual tests were spot checked (repeated somewhere else on the drive).
In researching this, it wasn't a matter that my car is "faster", stronger, or just plain cooler. It's a function of the drag of the vehicle and the RPMs the engine is turning.
Most cars make their best fuel economy somewhere between 1800 to 2200 rpm. Ah ha! My car has a 6 speed stick. If I'm in 6th gear it's turning about 2000rpm at 85mph.
I then compared ground speed to engine speed ratios of other cars, partly selected because they were owned by people in the discussion, or because they were fairly common cars. Depending on the vehicle, it's best cruise speed could be anywhere between 45mph to 90mph.
Serious? Seriousness is well above my pay grade.
But I've noticed I get less tired if I walk rather than run :-)
The people I encounter who are going noticably slow in areas are using MPG as an excuse to be self righteous, and block lanes of traffic. Its just another ploy for some to see how much they can get away with annoying people.
I wish people would use logic when they over take people. There is absolutely no reason to over take under dangerous conditions and, unless you're on a motorway it won't actually help you.
Thrashing your car and risking everyone's lives for a few seconds will not make up for driving slowly for a few minutes. It's not hard to prove either as anyone with a GPS tracker can see how little over taking does for your over all time but the damage it can do to your engine (and maybe your life) are greater.
As far as fuel efficiency, I think maintaining a constant speed, whether it be 30 mph or 50 mph is more efficient than going up and down. Since most people usually vary their speed for things like over taking and beating red lights and they may normally drive slower than I suppose the fact their trying to be consistent, even if it's at an annoyingly slower speed, are benefiting.
I've got a Honda Civic Hybrid. And have I ever gotten to love the mileage!
At 75, the mileage drops down to ~45 mpg. I haven't tried extended driving at lower speeds - which you really need to do to get a good handle on mileage so that you average out grade and wind factors.
But the biggest factor affecting my fuel economy was being able to look at the world situation, understand the concept of peak oil, and understand the effect that a developing world would have on existing fuel supplies - which led me to buy high mileage automobiles.
That is why I routinely get mileage in the high 40's to very low 50's.
The obvious answer that everyone seems to be ignoring is that you get the best fuel efficiency by not going anywhere at all. Thus we should all become hermits and all turn our cars into permanent drive-in theaters in the back yard. The stat I've heard before on fuel efficiency is 90km/h or ~50mph, but JWSmythe's comment makes sense also.
Make those fuel consumption displays mandatory.
Most cars these days know their consumption - it's one of the first things they look at when they connect the laptop to the engine when you go for a service.
Make the display mandatory, make it large, and put it in a prominent place. It'll do wonders for everybody's fuel consumption.
No sig today...
An American Road & Track issue from many years ago (and I'm damned if I can recall which one) had a long article on the results of some fuel economy studies conducted by BMW.
The findings seemed to show that driving style was more important than overall speed.
The tips, in general, were:
- Keep your speed constant; fluctuations up and down are bad.
- Accelerate to your target speed quickly. Spending time slowly accelerating up to it wastes fuel.
- Be in the highest gear feasible for your engine type and road speed.
- 75% throttle for acceleration, conditions permitting.
- Keep your revs low, and change gears often to keep them low. That said, know your torque curve, and use it; if you have a small 4 cylinder, trying to accelerate at 1000 revs is futile.
Using the holy grail of OSes...
Do like everyone else does, drive about 6 inches behind me at 65 mph.
There are sweet spots for driving which is usually specific to the type of vehicle, the gearing, etc. so, to an extent, I'm sure the faster you go the better MPG you will see. But for my car, Mitsubishi Spyder, they recommend shifting into 6th at about 50mph. So basically my interstate driving is all in the top gear by far. At 70-75mph driving on WV interstate highways I get about 20-21 MPG. If I just drop my speed to 65mph everywhere I go during a tank of gas I can reach 24 MPG. I've consistently seen those results out of at least the last 3 or 4 tanks of gas over the last couple months. If I take a US Route (speed limit 55) for 90 minutes to visit my parents my MPG goes up even more for that period of time because I'm going even slower than my usual 65-75 mph. I don't drive too much slower than the posted speed limit (5mph as I state above) because I don't want to feel like I'm crawling but just dropping 5 mph makes a noticeable difference in the range I can achieve with my tank (17.7 gallons). YMMV.
this nation, under God, shall have a new birth of freedom. -- Lincoln, Gettysburg Address
I have a realtime mileage display and variable cylinder technology in my car, and what I have noticed is that I can easily cruise at 75mph on 3 cylinders and get tremendous mileage in the process. However, when I hit an uphill grade, if I try to maintain 75 the other cylinders kick in and my mileage drops dramatically (to roughly 2/3). But, I have noticed that if I gradually back off on the accelerator while climbing the grade, bleeding down my speed to keep those other 3 cylinders from turning on, I can climb the hill while maintaining my high mileage. I've learned also to accelerate slowly on level and mild up grades (like near the top of the grade) without the other cylinders engaging. Obviously when going downhill I take full advantage and build my speed back up while still getting great mileage. Perhaps something like this is what you are observing? BTW, I don't play these games in heavy or rush hour traffic; I only use these techniques when traffic is light.
There are lots of little things you can do to save on gas. Many center around efficient stopping.
For example, if I see a red light coming up, I'll often ease off the gas and coast in rather than maintaining speed and then braking near the light like most people do. In addition to saving gas on the way to the light, if the light turns green before you stop then you've also saved the gas it would have taken to accelerate back up to speed.
This tactic can be quite entertaining if, for example, an impatient bozo in a SUV comes up behind you while you're coasting, honks, pulls around you and speeds ahead only to stop at the light, and then you smoke him as you coast through the light just as it turns green.
First 100 miles after filling the Prius and mostly interstate going 70-75 mph with moderate lane-changing in moderate traffic got 50.2. Did a back-highway trip this spring of 300+ miles mostly holding to the local 55-ish while driving "Priusy" and the mileage for that tank was showing 52.1 when we got home. So I'd say not a huge difference based on various top legal speeds.
In a small, aerodynamic car, speed doesn't matter that much. (In a larger vehicle and especially trucks, with their poor aerodynamics, speeds above 60 do start to affect mileage more strongly.)
But how vigorously you accelerate can make a big difference. In the worst of the gas price spike I made a point of accelerating gently and shifting much earlier than usual, and found my mileage improved by 15%.
Your god may be dead, but mine aren't!
In bottom side of the scale, you can walk, is slower than 30mph, but in reasonably short distances is not that bad, and is healthy even. Or drive a bycicle, that is faster at least. Public transportation could be another cheaper alternative, if fits.
Only use a car/gas just when you need what comes with a car (and if what you need includes speed, then will be no slow driving saving anyway)
Slow acceleration is worse than (reasonably) rapid acceleration. The rest of your tips I can't argue against, but I do know that decent acceleration outside of the red zone is better.
Oh, for mod points. Most people (well, most men anyway) are competitive, and we like to beat our "high scores". Tachometers show us speed, clocks show us time, but neither of those contributes to efficiency. Adding a fuel economy display gives a better goal to beat.
If you were blocking sigs, you wouldn't have to read this.
I personally have been using the inertia of the car rather than selecting a particular speed as the 'efficiency speed'. I've gone from 9km/l to 12km/l. I've added 200 km to my 55 litre tank around town by driving up to the speed that will get me to the next point of change without a loss of noticeable time spent driving. I originally based my idea on the Toyota Prius which I had driven for ~ 12 months as a taxi driver. I deliberately practice consideration i.e. I don't do it if it is against the general flow of traffic or drivers are unable to get round me. Gordonjcp has it right, and practice consideration that other drivers may not understand what you are doing so get out of their way.
Semi-automatic amateur armchair Australian philosopher; conjecture ready at any moment...
Buy a Scangauge 2. Google it. It costs around $150. Hook it up to your car, and it will show you shitloads of fuel economy information and more.
Driving slower can help improve your gas mileage when there are a lot of stops. For example if you drive 10 blocks and you get up to 45mph and have to stop you will use more gas than if you only got up to 30mph and then stopped.
Doctors do Massage in Longview WA now, who knew?
A lot of people haul out the old 55mph chestnut when economy and fuel efficiency is brought into question, and the simple fact is that the 55 mph law was put into effect when very few cars had overdrives or auto transmissions with more than 3 forward speeds. Since the law was repealed, cars, engines and transmissions have been designed and improved to work optimally at higher speeds.
This is a sig. It is like every other sig in the world, except that it is mine, and it is different.
Air resistance.
Tyre rolling resistance.
Then approximately in order you have;
Air conditioning off.
Engine RPMs constant and at the peak of the torque curve if you can.
Clean your air filter.
Fit iridium spark plugs.
Use a fuel with a cleaning agent every 6 months or so.
And probably illegal;
Chip your car so it runs at the ideal gas/air mixture, not simply one which will allow it to pass the regulations.
Get rid of your catalytic converter.
Deleted
Related: are there any practical hypermiling techniques that you've found for people not ready to purchase a new car, nor give up driving generally?
Drive downhill.
Gordonjcp http://ask.slashdot.org/comments.pl?sid=993269&cid=25348749 is wrong about efficiency. It does make a difference to fuel economy, at least in my diesel ute. Just as turning off your engine if you are likely to be at a stop light for >10 - 20 s does save fuel. I've been recording the numbers for over 6 months and it has increased efficiency. I haven't had a chance to do it in a small fuel efficient car (barring the Prius of course), but it definitely works in the Rodeo.
Semi-automatic amateur armchair Australian philosopher; conjecture ready at any moment...
I'd say the way people blast off from the green light like their in a Formula 1 Grand Prix* is probably doing a bigger number on fuel economy in city driving more than anything else.
* or not if you were Hamilton yesterday.
"The great thing about multitasking is that several things can go wrong at once." -me
Good luck trying to go 55 much less slower on I-294. The people who go slow like that are the same people who wasted gas by idling and holding up traffic.
It's counter-intuitive, but relatively rapid acceleration is far better than slow acceleration.
A long, slow acceleration up to a target speed will use more fuel than a rapid acceleration up to a target speed. This is regardless of the vehicle's horsepower or torque.
Downhill coasting I've covered in other posts in this thread. Suffice it to say that brakes are a safety feature that you don't to have missing in an emergency.
Using the holy grail of OSes...
While wind resistance scales with speed squared, the simple fact is that most of the energy wasted in a car is in stopping, not wind resistance. Normal driving around the city I can get 19-22 MPG, and I use smart braking like the parent discusses. Driving 65-75 MPH across states (where I am just GOING), I can get almost 35.
If someone has already said cruise control, I apologize for restating it, but for me it works. The computer in most modern cars can control the speed of the car within a 20th of a mile. (1/20) That is a lot closer than any human can handle. This prevents you from over/under speeding (I.E. You wanting to go 70 MPH but you waiver between 68 and 72). There are other obvious things you can do though: regular car maintenance being the biggest of them all
Walk back up?
Just never go back?
You can also try bricks to hold the accelerator pedal. I've found that mileage may vary, however. After all, you would need a 60 mile per hour brick, 70 mile per hour brick, etc.
I always thought those people were assholes, and I'd fly into a rant about how dangerous and reckless that behavior was. But they're just trying to save money. People really are basically good after all!
Oh, yeah, it's not easy to pad these out to 120 characters.
I've been car-less all my life. We rent a car when we need one. ~$100/month spent on a car. Live urban, not suburban, and this will be easy.
Schfifty five?
DRM: Terminator crops for your mind!
with a manual transmission. I got it new (picked it up on 9-11-2001 -- felt like a schmuck picking it up that day, but hey, I needed it!). For years I drove as fast as I liked (almost always 10 mph over whatever the speed limit was). For 6 years I averaged 34 to 36 mpg. Then this spring I passed a guy in a Saturn. He was doing 55 mph in a 70 mph zone. He had a sign in his back window that said something like "I'm getting 40 mpg driving at this speed -- please just smile and go around." I gave it a try. I had a long trip scheduled for the next week, and (honest) I got 45 mpg. I've been doing 55 on the highway ever since, and saving a lot of money. My wife is embarrassed to ride with me. She'll get over it.
I am not left-handed, either!
This is just another case where people don't realize (or care) that trying to maximize the performance of one part of the system (their commute) ends up diminishing the performance of the overall system.
Only a few people doing this slow driving will result in large numbers of other driver stuck waiting at more lights. Even worse, this kind of slow driving will result in some other drivers driving recklessly trying to get around the slow drivers. It won't take many crashes, injuries, and deaths to completely wipe out any savings made to the economy by a few people driving slowly (if only from traffic backups due to crashes).
Using these kinds of hypermiling techniques are just fine for an individual who doesn't have any regard for how their behavior impacts others.
Most of my miles are non-highway, over 1/3 of them are on a bicycle.
Non-highway, the name of the game is to figure out if you're likely to be slowing down ahead, and if so, immediately take your foot off the gas. The only time accelerating pays off much is if you make a light that you would otherwise miss. I have not yet done the turn-the-engine-off at stop-lights experiment, but my understanding is that if you are stopped for more than a few seconds, you win. However, since my starter might not have been designed for that sort of use....
I'm little surprised to read of higher efficiency at much higher speeds, because wind resistance is a bear. To shave 10% off my bicycle commuting time, I must put out 30% more power (but for 10% less time, consuming 20% more energy). When the power is coming out of your own hide, you do notice, and don't need some silly magazine to tell you that you're working harder. The difference between 55mph and 80mph is a factor of TWO in the energy expended -- is the engine really designed to be that much more efficient at the 80mph RPMs?
Postet this before and got heat for the turning off down-hill. I am doing it where possible and I feel like - you can do what you want, not my business.
There is no question that coasting with engine off uses less fuel (zero) but there are other legitimate questions:
Is it necessary? - in many modern cars the fuel is cut off while engine breaking, so in that case you are using zero or thereabouts fuel anyway. On the other hand any savings on fuel (if any) can be easily offset by the extra wear on the brakes. You could also cause major damage to your transmission if you shift into a low gear or even into reverse by accident while moving at high speed.
Is it safe? - No. It's a bad idea to drive in neutral as you cannot quickly accelerate should the need arise, and also increased strain on the brakes makes it more likely that they will fail at the wrong moment.
Is it legal? - Depends where you live, in California and probably some other states it is actually illegal - look up California Vehicle Code 21710
Negative moral value of force outweighs the positive value of good intentions.
The major key to fuel economy is not to brake much. That's when you're throwing energy away. Unless you have something like a Prius, with regenerative braking. Pay attention to traffic lights ahead of you, and coast up to red lights without braking if possible. Pay attention to traffic light synchronization. Many lights are synchronized, at least for a few adjacent lights, for a specific speed. Often, you can drive through a whole set of lights at a fixed speed without stopping. Allow extra space ahead of you and use it to avoid as much braking as possible.
For an amusing example of this, see the Great Highway in San Francisco, which runs for several miles along the beach with no place to turn off, but frequent traffic lights at pedestrian crossings. The traffic lights are all synchronized, and if you drive exactly at the speed limit, you should never have to stop. But watch driver behavior there. Even in this ideal case, people are speeding up and slowing down.
For internal combustion engines at low speeds, heat loss, the "idling cost", within the engine dominates. This is not true of electric motors, which have no idling cost This is why electrics do so well at low speeds.
At a fixed speed, rolling resistance and air resistance dominate. Tire pressure matters far more at higher speeds. Air resistance goes up with the square of the speed; below 30MPH or so, it barely matters; at Formula I speeds, it dominates everything. (Formula I racing cars are using maybe half their energy in the airfoils used to push the car down into the road to get more traction. However, a spoiler on a passenger car is a lose below 90MPH or so.)
It is all about the RPMs that the engine is doing. The more RPMs, the more times fuel is injected into the engine and burned per minute. It is really that simple. If your engine has a good gear ratio, maintaining speed at 2,000 RPMs at 50mph will be better fuel efficiency then 45mph at 3,000 RPM in the previous gear. However, that said, a 4 speed automatic won't usually be able to shift into a higher gear at a lower RPM than what is set in the computer to begin with, which is why manuals get better fuel economy than automatics (well that and the fact that the "manual" can shift gears ahead of changing conditions since the control mechanism can usually see a 50-100 feet ahead of the vehicle, whereas an automatic can only see the road that thing it is currently at).
We were all warned a long time ago that MS products sucked, remember the Magic 8 Ball said, "Outlook not so good"
I realize that "slowing down" may seem like an obvious tactic to some (and maddeningly annoying to others), but there are plenty of other ways to save fuel costs... improper tire pressure, improper alignment, excess weight in the trunk and others are documented and explained there (I count 13 other things in the article linked here).
Give it a read and pass it on, you might help others conserve as well.
There are a lot of factors.
Drag does up with speed, and is non-linear and vehicle dependent (a low drag car tends to also increase slower and later)
Other losses (drivetrain, tyres etc) tend to increate, some with RPM, most with speed.
Road surface makes a difference!
Engine efficiency is the complex one, engines are very inefficient at high AND low speeds.
for a first-order approximation, your engine is probably (depending on design) most efficient at the lower end of its torque peak.
However, the #1 difference is driving style.
The most efficient styles of driving can be VERY surprising - accellerating at the torque peak until a speed above your target and then coasting slower is one of the best, but a real pain to do.
Even for normal driving styles, a variance of 20% is not uncommon, especially in city driving.
The upshot is that slow driving is not by any means the answer to fuel efficiency. ;)
Fast driving is even worse though
#1 rule of fuel efficiency, learn how to drive your car, and get a realtime fuel consumption monitor, log each tank of gas, and learn!
Let them think driving 30 in a 45 zone will give them better mileage; maybe we'll have a heckuva lot fewer deaths.
Or, people will still drive just as stupid and it won't have an effect.
Need an automatic screenshot taker? Try here.
Unless you're in Oklahoma, in which case you use brakes only for emergencies and also reflexively at the top of every fucking hill and during any curve (no matter how slight)...
I just purchased a Prius this year. Not with the idea of saving money on fuel (I'll never save enough to make up for the cost of the vehicle.) but for environmental reasons. However, having a car that gives me constant feed back about what mileage I'm getting has made me change the way I drive.
I do drive more slowly. Not because my mileage goes up from the lower speed but because I like more distance between my vehicle and the vehicle ahead of me. It allows me to take my foot off of the gas and coast when the vehicle ahead brakes. If I can slow down by coasting rather than wasting my momentum by braking I'm saving gas. Many times the car/truck ahead will brake in order turn onto a side street. If I don't have enough distance I have to brake myself. I try to anticipate and slow down on my terms.
Also I don't stomp on the gas peddle to accelerate. Gas mileage is horrid during acceleration even in a Prius.
In the US the Prius doesn't come with a EV mode. Although the computer is aware of that ability, US customers are not given a way to engage EV mode as they are in Europe. There are many hacks that allow a person to access this mode and I have installed one but find that the short range (Less than two miles.) makes it almost useless. Even the next generation of the Prius that is suppose to be pluggable is only suppose to have an EV range of about ten miles. Still pretty lame.
The race isn't always to the swift... but that's the way to bet!
There have always been people that drive much slower than the posted speed.
I'm not sure if they are stupid or lost. But they do drive me crazy.
I don't think it has anything to do with saving gas.
Hybrids are becoming increasingly popular, especially amongst those who consider fuel consumption a priority. I just purchased an Altima Hybrid a few months ago, and I have found (circumstantially) that most of my gas savings come from lower average speeds. Driving above 40 mph or accelerating quickly forces the engine to be on, which cancels most benefits of a hybrid (in fact, the extra weight of the electric motor and battery can actually reduce mileage compared to a non-hybrid.)
The best hypermiling technique I've found that anyone can do is don't be aggressive on the road. This is pretty obvious but I used to drive like a jerk and weave in and out of cars, constant slamming on breaks and jamming the accelerator. Then gas hit $2.50 and I had a baby on the way so I dramatically changed my driving habits. I coast a ton and never tailgate (well, I do draft behind semis sometimes on the highway). My MPG has gone up a ton and I was basically paying the same at $2.00 and $3.00/gallon for a tank of gas. I do mostly city driving so it's tougher to keep a constant 55 MPH (seems to be my optimum speed), but I just don't drag race from light to light anymore.
Reviewing just the first hour of video games.
And while you are at it, tune your carburetor.
Modern ECUs already turn off the engine when you are coasting down a hill. Fuel injectors don't have to inject something every time the intake valve opens.
I had a Subaru that wouldn't start putting fuel into the engine quick enough, so every time it the engine was really cold and I pushed in the clutch after going down a hill, it would stall.
If I have nothing to hide, don't search me
I usually manage the first fifteen miles or so without touching the brakes once on the main road -- there's no acceptable way to slow down enough for the toll bridge without the brakes.
Other things I've tried:
I don't have any hard data on how much this is helping -- but I do seem to go farther on a tank of gas than I used to. I generally get about 30mpg combined. ('97 Escort wagon w/automatic)
Paleotechnologist and connoisseur of pretty shiny things.
There are simple driving habits you can do to save some gas.
#1, anticipate when you have to stop. If you're cruising along at 50mph on a country road, and you know there's a stop sign up ahead, get off the gas early, and coast down, so you start applying your brakes at 25mph instead of going straight from cruise to braking. Traffic lights are harder, but if you can anticipate the timing, you'll coast up to the light as it's turning green, instead of going full power up to it and then braking to a stop, and then having to expend all that energy to get moving again. Similarly, slow down early for curves - just coast down, instead of having to use your brakes. Regenerative braking stores and reuses this energy in these situations - without it, you have to not use the energy in the first place.
#2, work with hills, not against them. When going up a hill, don't downshift. Use a max of 75% of your engine's power in high gear, and accept that it's OK to lose a little speed. Reach the top at 35mph, go down the hill and pick your speed back up to 45, and then burn it off again going up the next hill. This lets you keep your engine at efficient lower revs, and reduces energy wasted in braking. It's easier with a stick shift, but in an automatic you can learn how far you can push it without downshifting.
#3, don't bounce the throttle. A lot of people constantly move back and forth between 0% and 50% throttle to regulate their speed, instead of just pushing to 25% and holding there, and letting their speed wander 1 or 2 mph up or down, or gently adjusting the throttle by 5%. Your engine's computer fine-tunes fuel-air ratios best when it's running steady state; when you make lots of fast changes, it has to make lots of guesses about fuel flow, and it errs on the side of too rich (preventing damage to the engine at the expense of wasting gas). This is why cruise control tends to save gas (it makes slow, smooth throttle adjustments), but I've found I'm easily able to do better in many situations, especially combined with #1 and #2 above.
#4, understand your MPG meter. Some people are bothered that they get single-digit gas mileage when they're accelerating, so they accelerate REALLY SLOW to make their mpg always stay above 15 or so. 15 MPG for 30 seconds is actually worse than 5 MPG for 10 seconds (you spend more time in lower gears), and you're screwing up traffic flow when you do it, making everyone behind you waste gas too. Step into it (say, 75% throttle, shifting at 60% of redline in a normal family car), accelerate up to speed quickly but smoothly, and then get into high gear and start reaping your cruise mileage sooner.
In all of these techniques, pay attention to your effect on traffic around you. Big gains can be had with relatively subtle changes. If you're varying your speed around too much, you're obnoxious, dangerous, and wasting everyone else's gas trying to get around you, so stay aware of what you're doing to others.
downhill coast and turn engine off (you gotta know what you are doing - PS fails and break booster as well after a while)
I think in older cars that might work. In newer cars its not a good idea because:
a) they already cut of fuel intake when coasting
b) when you start it back up like that, unburned fuel can get into the catalytic converter and seriously damage it
are there any practical hypermiling techniques
Acceleration is the killer (or hitting the gas to go uphill). If you keep your speed as constant as possible, you'll minimise fuel consumption more than by any other technique. On the open road, 50mph seems to be about optimum (car magazines use this as the test speed for consumption). In city streets, I guess 20, but it's going to vary according to congestion.
This means you'll want to avoid having to brake suddenly (because that means accelerating again to get back to your ideal constant speed). which is why you might see people driving more slowly than usual: not to save fuel per se but to give them more reaction space and minimise braking.
My father told me that during and after the war, when fuel was rationed, his father used to turn off the engine when they got to the top of a hill, and roll down, starting again near the bottom by switching on the ignition, putting it into 3rd, and letting out the clutch (works only on a manual, of course).
Are you relying on some sort of in-car display or are you actually measuring miles dirven and gallons consumed?
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
I drive a Toyota Sienna minivan. When first got it I drove in the fast lane at 65..75 mph and was getting about 22 mi/gal. I've moved to the slow lane and now usually am at 55..60 with the cruise control on. I let the testosterone-crazed go around me instead of driving fast enough to keep them off my rear bumper. I leave a large gap and try to avoid braking. I'm seeing 25 mi/gal in these conditions. The (automatic) transmission doesn't come out of lockup even when maintaining 55 uphill. Next step is to remove some of the rear seats to lighten the load.
I won't recommend it for everyone, but this spring I got one of those generic Chinese-built 50cc 4-stroke scooters, which is running a fairly consistent 118 miles per gallon (or just about 2.0 liters per 100 kilometers). On the plus side, many states exempt or simplify the rules for 50cc engines, and the total price of the generic models are 1/4th the price of the trendy brand names like Vespa or Honda. On the minus side, besides the extra risk due to stupid "cage drivers", these generic brands take a bit more self-maintenance and self-reliance. I have a nice eight mile commute that I can cover on back roads, so it's been very pleasant all summer, saving me hundreds of dollars on the gasoline already.
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to keep your tires inflated
What?
Lets get one thing straight- by coasting (putting the clutch down and rolling) the engine is using the same amount of fuel as idling which is high MPG but isn't the best. By engine braking (using your gears to deaccelerate slowly) you are effectively using zero fuel- at least in most modern cars.
Obviously you could argue that the most fuel effective way to drive is to actually turn the engine off when going down slopes. PLEASE DON'T DO THIS. The reason being (my little anecdote)- I was in a car once my friend turned his engine off at the top of the slope. Stupidly not realising that the breaks are dependant on the pressure which is maintained by an engine running. Needless to say when we needed to brake properly we couldn't- luckily we realised before it was too late and switched it back on.
There are many factors which you can consider to save fuel:
- Keep tire pressure high - by doing this you are creating less resistance on the road.
- Remove unnecessary objects like roof racks which would effect the aerodynamics increasing resistance of the vehicle.
- Unnecessary luggage/weight in general.
- Use higher gears as much as possible. - Windows as cooling are better at saving money than using A/C at speeds under 50mph if my memory serves me correctly.
Fueling up
- Only fuel up half a tank - by doing this you could save yourself a lot because the weight of half a tank of fuel unnecessarily being carried around especially when you do the same route every day and can easily predict the best times to refuel.
- Use www.petrolprices.com (UK) to check for local prices if your wanting to save money.
- I met someone who once said that they only fuel up at night because at night it's colder and fuel expands therefore they get more from the pump. I'm not sure how the pump system actually works but I thought it was an interesting point.
AA tip website: http://www.theaa.com/motoring_advice/fuels-and-environment/drive-smart.html
All animals are equal, but some animals are more equal than others.
1) Inflate tires properly. If you don't mind some increased stopping distance, overinflate some. If you're rated for 35, consider 40 or even 45. It's not in danger of explosion, but you might see less tire in contact with the road, so the stopping distance might go up some.
2) Take the foot off the gas whenever you anticipate the need to slow or stop. If you take your foot off the gas early and coast down to 20 so you don't need to stop at a red light, you burn less gas than staying at 55 longer and having to accelerate from a stop. As a corellary, increase stopping distance in traffic whenever you don't see brake lights (traffic speed minus 1 or 2 mph), decrease when you see brake lights (but maintain safe distances). This will absorb some accelerations and remove some braking in addition to improving overall traffic flow.
The best thing you can do to improve fuel economy is educate the loose nut behind the wheel. Smooth starts, easy stops, realize every acceleration hurts, especially up a hill.
1. Drive like your car has no brakes. Visualize the speed you'd need to not have to touch the brakes due to a slowing of traffic, a traffic light being red, etc. Accelerate to a speed no faster than that. Constantly update this visualized estimate as you drive.
2. For any given target speed, drive in the combination of the highest gear and the lowest RPM that doesn't lug the engine. If you have the space and available speed limit to go a gear higher, then do so. Note that at some point you will hit a gear where wind resistance takes over and reduces your fuel economy.
For #2, you'll need a scan tool with instantaneous fuel economy readout in order to find this gear for your car. Borrow one for a short period if you don't want to buy one. Similarly, you might want to borrow or buy a scan tool in order to refine your "lowest RPM" number, as going as low as you can without lugging it is a good place to start but there may be a sweet spot slightly above that which has even better fuel economy.
As a bonus tip: Learn the stop lights during your regular commute that will force you to idle for more than, say, 45 seconds. Turn your car off when you stop at these intersections. Obviously, if you get to the intersection late in the stop light you might as well leave it running, but that aside you'll quickly learn that there are a lot of times during your commute where you idle for a long time, and idling (as well as creeping) are terrible for fuel economy.
PS - I've already seen one poster mention using engine braking instead of brakes. Ignoring for the moment that doing so would have zero effect on fuel efficiency, I'd like to share a maxim that I learned re: engine braking from a trusted mechanic ages ago: brake pads are cheaper than engine rebuilds.
This tactic can be quite entertaining if, for example, an impatient bozo in a SUV comes up behind you while you're coasting, honks, pulls around you and speeds ahead only to stop at the light, and then you smoke him as you coast through the light just as it turns green.
Oh, please. I drive a large, heavy SUV (when I drive, that is - I don't have to commute, unless there's actual smoke coming out of something in the rack at the datacenter). I'm the guy coasting to red lights (which REALLY makes a difference in mileage, since my vehicle seems to be able to coast for about a mile)... and the impatient jackasses riding my ass, honking, and accelerating past me to the red light are almost always 21-year-old arrested-development twits in 1-inch-tire Hondas with stick-on ground effects and kazoo exhaust systems. They just can't wait to get that red light where they can sit and goose their kazoo noise makers, using more gas making musical exhaust sounds than my SUV does simply idling. And then when the light turns, they dig out as fast as possible so that they can angrily wait at the next light, too. That's OK, I'm the villain, right?
Don't disappoint your bird dog. Go to the range.
..is accelerating relatively fast to something like 70mph,
then pull of the engine and roll with no gear until You reach
something like 10mph when You start the engine and repeat.
This is the empirically show best method.
But it will probably irritate other drivers...
Mundus Vult Decipi
...then whatever entertainment value is thankfully and rightfully lost.
Twitter supports and protects racists - by smearing their critics with the "Hate Speech" label.
I Have a Big Holden Acclaim V6 3.8l engine, my wife has a Small Holden Barina 1.6l engine. We both use E10 (10% Ethanol) from the same pump. Now here is the surprise she gets 10L/100Km I get 12L/100km (I have had it as low as 8.2L/100km on a 1 hour 100km/h all the way trip) and I mostly do city driving (short trips to take our son to his carer then the station).
Now you would think with an engine over twice the size of my wife's car I would be using a hell of a lot more. Well at 100km/h my engine is doing only 1700-1800rpm while at the same speed her engine is doing 2400rpm. Taking off from the lights at a reasonable speed (not smoking the tires up) I push about 2200-2400rpm, to do the same in the wife's car your pushing 2500-3500rpm
On a flat road the smaller car is ok, but through some hills in and the bigger car cruses up them easy in top gear, the smaller car drops back a gear (or 2) and uses more fuel than the bigger one.
So a smaller car doesn't mean better fuel economy.
Some simple tips;
1. don't over accelerate (rev engine more than the automatic can transfer to the wheels).
2. find the optimum torque to revs and don't go over it.
3. Use the highest gear you can, but don't short shift, it puts too much strain on the engine and reduces its life.
4. Use cruise control where you can, some cars have special shift zones for cruise control that reduces fuel usage.
5. Where possible take longer to slow down/stop your breaks turn all that energy you used to get to speed in to heat and wastes it.
Other tips;
Here in Australia we have a price rise cycle, the price is lowest price is the morning of the day before Pay Day (when most are paid) where it can be $AU0.15 / litre cheaper than it is that night. So find your cycle and have a credit card or the money to get it at its cheapest.
In Australia we also have E10 (10% Ethanol) which is 95 Octane compared to 91 Octane for regular unleaded. I have found in my V6 3.8l I get about another 50km per tank city or 100km per tank in country.
Puggs
Access Point Live Mapping Access Points with Google
From what I've been told, MDS only kicks in at highway speeds (over 50 MPH if I remember correctly). Personally I think there should be an automatic and manual mode, so the driver can make a choice if they want to.
As a practical matter, outside construction zones, I-294 has no speed limit.
paintball
Hypermiling isn't even remotely about slow driving. It is about accelerating at an optimal rate, cruising at an optimal rate, and carrying no more speed than necessary to get to the next known stop.
Pay special attention to that last one. Carrying no more speed than necessary to get to the next known stop. A hypermiler's behaviour isn't going to affect anyone. If they were all going to be stuck at the next red light, they were all going to be stuck at the next red light. If they were going to make the light, everyone can cruise at their optimal rate.
A hypermiler's behaviour only impacts how other drivers _think_ they are doing in terms of making good time to their destination. Such other drivers love to do things like see that a light is turning red and then _accelerate_ towards it because they want to be first in line. Or because it just feels good. Or whatever. But they'll be waiting at that exact same red light as everyone else, including the hypermilers.
Posts like yours place the blame here on the hypermilers, but the blame should reside elsewhere.
Oh yes. My car's got one of those displays and my fuel efficiency is about 10 MPG higher than it was when I first got the car, because I pay attention to how my driving affects efficiency.
Maybe in your area someone going 30 in a 45 zone is trying to save gas, but here it's just another idiot looking for a particular street to turn down.
I recently bought the Scan Gauge II and have been playing around with different driving styles. Sure, it's possible to squeeze better mpgs out of my car, and I admit that it's kind of fun to try to get it as high as possible. Most tricks, however, are only really academic, and probably not worth the effort. Meaning, yes, it will marginally improve performance, but not enough to justify altering your driving habits. Pennies saved over your commute is not worth the effort or safety risk some of these tricks require. But from my experience, I've come up with the following rules of thumb:
1) Don't drive like a Dick.
Drive the speed limit when reasonable. Don't tailgate. Don't accelerate like a maniac. It's amazing that these three rules of "not being a Dick" also happen to be three of the best mileage savers.
2) Avoid unnecessary breaking
This is kind of a mis-statement. Breaks are important. And for God's sake, please do use them. Always break when you need to. But, when you do use those breaks, think to yourself: Why did I need to break? Was it to stop from hitting the car in front of me? If so, was I using too much gas to begin with? If "yes", then, you were wasting gas. You spent the energy to speed up, only to waste it by breaking. Basically avoid (again, when reasonable) getting yourself in situations where breaks are needed. Oddly, it almost comes back to "don't drive like a dick".
3) The A.C.
Be comfortable. But if you're driving on normal roads and you can have your windows down, go for it.
4) Carpool, walk, public transportation etc.
Not driving is INFINITE MPGS!
Eh - do yourself a favor and google for "fuel saving slow acceleration" - without quotes, so you can figure how dead wrong you are:
Accelerate Smoothly: By accelerating gradually and driving smoothly, you could increase MPG by as much as 20%.
But 45 miles per hour does not imply highway driving. It implies driving where the car must stop every mile or so. In this case the energy distribution is different, the dominant term probably being the energy needed to accelerate the car to cruising velocity, which, at 40 miles per hour, with 1 mile stops, occurs perhaps every two minutes. The energy of a car moving with a mass of 'm' moving at 'v' miles per hour is on the order of mv^2. This means that accelerating a car to 45 miles per hour will require twice as much energy as a car that is kept under 35 miles per hour. Now if one is talking about a small car traveling less than 25, and big hemi traveling at 45, then we are talking 4 times as much energy to accelerate the car every few minutes. Of course with a hybrid car some this energy is recovered, but then the rate of acceleration is factor. The faster one accelerates, the less adiabatic the operation, and the less energy is recovered.
So to summerize. In the city, a hemi truck accelerating to 45 miles per hour requires maybe four times as much energy as compact traveling at 30 miles per hour. This energy directly relates to fuel consumption. On the highway where velocity is constant, the domanant factor is merely the energy to overcome friction, which primarily depends on how the engine is constructed and how the shape of the car interacts with the environment. This will probably be slightly different for every car, and every driving style. Thirty years ago it appeared that cars were built to go 80 miles per hour for maximum efficiency. I think it is criminal to drive a Porche slower than that. At the end of the day, for highway driving, it would probably be best to monitor the tachometer for optimal fuel consumption rather the speed. For city driving, slow accelerations with higher speeds only on longer stretches or road.
"She's a scientist and a lesbian. She's not going to let it slide." Orphan Black
When a piece starts out with this you kind of get the feeling you're headed into a propoganda piece.
Kind of like stating emphaticly up front " I haven't a clue , what I'm talking about".
And yes , driving faster lowers miles per gallon, Wind resistance and all that.
I can't remember if the resistance goes up as the square of the speed or the cube , maybe both (speed variable) but faster = less economical.
That's why you always want to have a tail wind.
Trying to improve MPG in cars and trucks, I have found, is an exercise in futility. Sure, using a few hypermiling tricks, you might gain something, but considering some of the tricks I have read, they are downright dangerous!
If you really want to get great MPG, get a vehicle designed from the start to get great MPG. I bought a Kawasaki Ninja 250. This year, I put 9,000 miles on it. Motorcycles, across the board, beat out most any car/truck. They put less wear on the roads and have fewer moving parts to maintain than cars.
The down side is, of course, you get wet when it rains. Suck it up, nancy boy, that's life. Sometimes, if feels quite good. For you folks in warmer climates, you have it best for motorcycle riding more months than northerners.
Insurance is also cheaper for bikes, than cars. It is a win-win-win all around.
Bearded Dragon
On the one hand, braking is bad. Whenever you have to brake, that's energy lost. On the other hand, people recommend drafting to pick up efficiency by letting the guy in front of you break the wind for you. But, when you're close enough to be drafting someone, you're going to have to make heavy use of your brakes as the guy in front of you speeds up and slows down. What to do, it's a dilema.
...I save fuel by biking most of the way to work. I started earlier this summer by driving most of the 20-mile distance, parking, then cycling the rest. Several months later I've settled on driving 5 miles and biking the remaining 15.
Honestly I've probably saved a very small amount of money overall due the the bike accessories I've picked up along the way, but I've got way more energy and lost several belt-notches.
Driving less than the full commute distance is probably not realistic for most, but something to consider.
Obviously this is anecdotal, but I can offer my experiences. Since 1992 I've calculated my mileage at every fillup; it's a habit now.
My ordinary commute is 30 miles, each way, in minimal traffic (opposite rush hour). The route is almost entirely interstate highway driving - I-280 & I-80, through Northwest NJ. The normal traffic flow runs about 75-80mph.
For a year I did this commute with my cruise control set to 70mph. During weekends I did general city - stop'n'go errand running. I routinely achieved between 22-24MPG.
This past May I dropped the cruise control down to 60mph, and also tried to alter my driving habits. I gradually slow down before lights or stop signs, and I accelerate more gradually from lights and stop signs. And yes, I pretty much live in the right lane on the highway.
My gas mileage immediately increased to between 25 and 27MPG consistently.
I've got a 2004 Mazda 6, with a 6-cylinder and a manual 5-speed transmission.
Basically, everything we've all been told all our lives about efficient driving - avoid fast starts, fast stops, etc... Don't drive aggressively - DOES in fact result in higher gas mileage.
I own two vehicles, a 1700 Yamaha Warrior which I drive daily, about 45mpg. But since I live in the bush, hunt and fish constantly and pull horses etc my other vehicle is a 2008 GMC sierra 1500 crew cab short box. This has the "displacement on demand" cylinder shutoff. It's a 5.3L slightly modified LS4 engine. I get around 16-17 mpg in the city and on the highway is about 18. The highway mileage is low for the truck because I have the 4.10 rear axle ratio. The 3.73 rear axle does much better, but you lose 1000lbs in tow capacity. The sweet spot is 55mph, which I can get 20mpg at with the cruise on. Of course, compared to the other trucks I've had on my life, this truck gets about 2x the gas mileage. We've come a long way! I wish I would have waited another year though, 2009 GMC is releasing a hybrid 1500-series ton truck. Bummer!
It doesn't matter how slow or fast your dumb ass goes as long as you travel without a lot of acceleration/deceleration. I get better mileage at 80 mph travelling at a constant speed than any idiot putting on his brakes every 2.5 ft travelling at 10mph. That's why cruise control works so well.
Excellent idea, it would probably cost $10 if it was standard equipment.
I seem to be using the same amount of gas to maintain a speed, be it 55 or 80. Obviously , at 80 I am covering ground more quickly, so the mileage ends up a bit better. If I have to brake and recover speed there is a huge loss, and if that is repeated too often then I lose all benefits.
1) Choose a straight and level section of highway.
2) Get up to the speed limit and take a reading of your tachometer's RPMs.
3) Reduce speed by 10% and take a reading of your tachometer's RPMs.
4) Did your RPMs go down by more or less than 10%?
If your RPMs went down by more than 10%, then you have better fuel efficiency at the reduced speed.
If your RPM's went down by less than 10%, then you have better fuel efficiency at the higher speed.
Wind direction, open windows, and the presence of hills will all have effects on your efficiency. You should strive to eliminate such differences when taking your readings.
I own a 2005 corvette so I'm fairly sensitive to gas prices since I am required to use premium gas. Here is how I how I changed my driving habits to go from getting 15mpg on average per tank of gas to 22mpg under practically identical driving conditions.
My 'vette is a 6-speed manual transmission and has both an average and instant mpg monitor. On the highway, my 'vette gets surprisingly good gas mileage; on average between 26-30mpg. Unfortunately the 'vette suffers greatly in stop-and-go traffic, which was my more common type of driving.
To boost my mpg, I adjusted the following driving habits:
1. Drive in the highest gear possible. I used to have a habit of driving in 4th gear around town. Switching to 6th gear on the same roads boosted me from 15mpg to 18mpg with that single change.
2. In general, reduce acceleration and brake usage. Many of the following items give specific examples of this basic theme.
3. Don't brake while making turns or taking corners. I used to brake heavily before taking a corner, followed by hard acceleration after the corner. Reducing both helped.
4. Coast to stops. Rather than keeping the foot on the gas then braking at stops; I coasted as much as possible with the clutch disengaged.
5. Observe and anticipate traffic-lights.
Anticipating a green light to turn red meant I could coast to the inevitable stop from a farther distance away. Good timing was a bonus since I might not need to stop at all. Rushing up to beat a green only to have to brake hard and THEN start from a dead-standstill just wastes gas. Might as well coast; it's all the same time-wise.
Anticipating a red light to turn green meant keeping my speed steady which avoided needless braking followed by needless acceleration.
Sometimes applying a little accelerator on a diminishing green light meant avoiding having to start from a dead stand-still at a stoplight (the worst gas consumption to avoid if at all possible).
It all comes down to paying attention to your traffic lights on your most commonly traveled routes and knowing their specific timings.
6. Find your sweet-spot on the highway. Turns out my sweet spot for my 'vette, mpg-wise, was between 75-85mph. Driving slower isn't necessarily more efficient.
7. Ease the accelerator from dead-standstills.
8. Get to your highest gear possible as quick as possible from stand-stills. I start in 1st and skip-shift to 4th and then skip-shift to 6th.
9. Keep the tires inflated.
10. Coast in parking lots. If you have regular places you go to such as shopping or work, find ways to coast into your parking spot to avoid using the accelerator. Taking a few extra seconds to park (or parking a in spots that are conducive to coasting even if they aren't front row) isn't going to change your day but it will save you some gas.
Perhaps some of these tips will help you. I know they helped me.
Runesabre
Enspira Online
"the high gas prices and ongoing gas gouging in my hometown ... "
Price GOUGING, really?? Perhaps you'd better take a step back and learn some basic economics. I'd suggest _Basic Economics_ by Thomas Sowell. If supply drops, and demand stays constant, then prices have to rise - unless the prices are being controlled by the state.
Supply did drop - drastically - in North Carolina and the prices adjusted to prevent huge shortages. Unfortunately, Governor Easley instituted his "anti-price gouging" laws, which artificially kept prices low and thereby caused massive shortages.
What's better - waiting in line for 2 hrs to get $3.70/gallon or filling up immediately for +$4.00/gal? What about in an emergency, or if driving is essential to your job? Yeah, good luck trying to run a business when you spend 1/4 of your day waiting to fill up w/ gas.
RobotBox - Robot projects from around the world
c) Power brakes and power steering means that braking or steering becomes very very difficult. Not safe...
We don't believe in radical loony monotheistic religions from the middle east -- we're Christians.
Who cares. Please get your welfare econobox off the fucking road. Those of us who make more than $2 a day have places to get in our gas guzzling v8s. Assholes!
Brake == those things that you use to stop your car.
Break == stopping doing something for a time, or splitting something in two.
What's especially confusing about your post is that it almost makes sense using the second word, until you talk of "Why did I need to break? Was it to stop from hitting the car in front of me? "
(I was only an egg, but then I cracked)
In fact i've found that i often learn how long the red lights are and can really optimize my timing and breeze through them at speeds pretty close to the limit.
I've observed the same SUV issue, its' great
I quit drinking and driving... and boy, that sure cut down on how many times an hour I got lost. Well... quit, more like slowed down. Hold on, I need to pull over. I see lights. Bastard's probably gonna tell me I can't text and drive. When are they gonna stop taking away our freedoms? Well, time to take out the ol' bottle of mouth wash! Over the lips and threw the gums, look out stomach, here it comes!
---You must excuse my ill mannered attempt at comedy. I've been watching theonion's news shows for the last 3 hours. Man, I need a life.
Some time (when the roads are quiet), give it a go and see just how far you can get without touching your brakes. Certainly don't put yourself in danger, but if you are observant and plan ahead then you can usually do just fine.
Low rotation is the key. The speed varies according to the vehicle. Your's is the speed you naturally (when driving smoothly, not when giving full power) shift to the highest gear. That's the rotation the engine "wants" to run at. Smoothly and gentle.
In my first trips with my motorbike, I was still learning, and driving slowly, around that ideal cruising speed (80 Km/h or 50 mph). The tank was sufficient for 240Km (150 miles). Now, driving around 100 Km/h (62 mph), it's empty at 190Km (118 miles).
factor 966971: 966971
I can point to a few charts pretty easily...
There's certainly economy to be gained if you drive a Geo Metro or Chevy/Suzuki/et al. spinoff:
http://metrompg.com/posts/photos/mpg-vs-speed-chart-z.gif
The improvement is much less dramatic, but still there, with a Honda CRX: http://xs205.xs.to/xs205/06352/Spdmpg.jpg
And lower speeds also make a big improvement with a Toyota Prius:
http://home.hiwaay.net/~bzwilson/prius/calculated_MPG_Rev_B.jpg
I haven't yet seen such a chart from any vehicle that improves economy with higher speed. I suspect you might get different numbers, however, with large trucks, SUVs, and the like, with engines so large they barely more than idle going 45MPH when not pulling a trailer...
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
I have experimented with my own hyper mile techniques.
For starters I drive a 02 Mazda Protege5. It's a 4 cylinder and it's a standard transmition.
I accelerate slower than normal. I shift at about 2,500 RPM instead of 3,000 (Unless I need to speed up faster like highway)
When on the highway, I drive 60 MPH and the speed limit is 65.
When going on a long down hill, I drop it in neutral. (Easier on a standard)
When I drive I refill at a quarter of a tank.
Before my techniques, I could go about 320 miles before needing to refill (At a quarter of a tank)
Now I can drive about 360 miles until I hit a quarter of a tank.
I say it works, and I don't hyper mile to the extend that it pisses everyone else off.
The greatest revenge in life is massive success.
I walk to work. It's fairly slow, but very fuel efficient. And as an added bonus, I'm in no danger of becoming a lardass.
One thing people don't realize is that if you drive 60 mph on the highway instead of 75, you can save so much in gas. If people were not in such a damn hurry.
The greatest revenge in life is massive success.
Check out http://www.cleanmpg.com/forums/ for lots of tips on how to squeeze the most out of a gallon of gas, no matter what you drive...
Here are some REAL NUMBERS - if you drive faster you _will_ have more drag and therefore consume more fuel. Yes, there are islands of greater efficiency on your engine and in higher gears you are running more efficiently, but these do not compare to the increase in resistance from driving faster. You can see real data from a 1998 VW Bug run repeatably and reliably for EPA testing here:http://picasaweb.google.com/waterppk/ResistanceNumbers#/ [Sorry for the crappy format, but I'm not going to post these on my website so you guys can nuke it!].
:) http://www.uwhybrid.org/ChallengeX/ http://www.erc.engr.wisc.edu/
Disclaimer: I'm a mechanical engineering student at UW-Madison, I'm on the hybrid vehicle team and am working on a masters in engine research
I doubt that the people driving 30 MPH in a 45 zone have done the math, but there is some sense to it. And like you suggest, the smart thing to do is avoid braking. If you have a 0.5 mile stretch of road between stop signs then accelerating to 45 MPH is just an extra 15 MPH to brake off at the other end. So it's not that 30 MPH is more efficient than 45 MPH on an infinite stretch of road, but the reduction of top speed decreases the loss to braking.
Except for a slight (~5mph) lead-foot on the freeway, I generally drive conservatively. But I decided to do some calculations based on driving from our office to our colo.
I have a compact and can expect around 31-32 at 75. Using the most optimistic measures I could find, I could up that to 42 by slowing to 55. So on that trip I would save about 0.6 gallons at the cost of 23 minutes of time.
If gas were up to $5/gallon, my break-even value of time would be aout $7.85/hour or about 15-cents below current California minimum wage - pretty bad ROI for someone working in high-tech.
This, of course, ignores the potential for accident, increased wear on the car, possibility of a ticket (though I have driven for decades without a citation), environmental concerns, etc. And it assumes one is driving alone - additional passengers increase the incentive to speed.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
It is said time and time again, but bears repeating: combine trips and reduce unnecessary trips. Miles times whatever mpg you get yields gallons. Less miles, less gallons.
As a (former) bicycle commuter, this seems to come naturally to me, but seems really hard for most other US car drivers who rack up an average of 15,000 miles a year. Beyond me how you do that without lots of unnecessary trips or drives across the entire country.
I thought I'd make a bundle coming up with the idea of giving cruise-control systems awareness of hills and allowing them to back off near the crest of a hill and accelerate a bit before the base a hill, but it's already been patented. The idea has been introduced, but I'm not aware of it ever catching on.
I suspect a major drawback to a company interested in promoting this system is that by design, it would introduce speed variances between equipped cars and non-equipped cars, which opens the door for accidents and litigation.
It doesn't make sense to go less than 50 if you are just cruising. But, in the city, you are basically constantly stopping and starting at stop lights or stop signs. In this case, going slower saves you energy because you use less energy to speed up (which is wasted when you apply the breaks in a non-hybrid vehicle).
All of this fuel efficiency stuff ignores the huge tradeoff you participate in when driving slow: time. For most professionals making a reasonable salary, the value in time you forfeit by driving slower is enormous compared to any difference in gas efficiency leading to lower fuel costs. Furthermore, driving slow imparts huge externalities on busy traffic, so you make the system as a whole much less efficient causing, in some part, slower driving for others who really do value their time more than gas efficiency.
I don't get it. Can someone put this in a computer analogy?
I found the following page on the EPA useful. It shows average and maximum fuel reduction based on temperature, head wind, hills/mountains, road conditions, traffic congestion, speed, acceleration rate, etc.
> are there any practical hypermiling techniques that you've found for people not ready to purchase a new car, nor give up driving generally?
Synthetic oil, 0W20 or 0W30, and change it at 3000km
Change the PCV valve once per year
Clean the battery terminal posts to make sure it's charging well
Check the belt on the alternator or the serpentine belt for wear
Change the thermostat every year to make sure the engine is operating at its correct temperature and you may as well change the rad fluid too
Narrower tires to reduce rolling resistance, maybe Run Flat tires and then get rid of the spare to reduce weight
Nitrogen filled tires to reduce leakage and corrosion of the wheel
Wash and wax the car, use a clay bar
Change the air filter, in the snow belt the salt dust that gets sucked in will absorb moisture and fluff up the filter, restricting air flow
Clean and regap spark plugs regularly, use dielectric grease to prevent corrosion
If your car has a distributor, open it and check the points and rotor for corrosion. Clean it or replace it, they're not very expensive.
Use the lowest grade of gas possible, Premium won't help in fact you'll get less mileage. The reason for grade of fuel is because of an engine's compression ratio, you dont' want the fuel-air charge to spontaneously combust you want it to slowly burn by the ignition of the sparkplug.
Clean the edge of the throttle body valve with a toothbrush and carb cleaner to prevent rough idle or hesitation when starting from a stop
If you need to run into the house, ATM, store for 2 or 3 minutes I've heard an automotive professor say leave the car on, the computer adjusts all the fuel-air mixture. Turning the engine off and on again will make it have to readjust, in that couple of minutes it's spitting out higher levels of CO2 than it would have if you just left the engine on.
Buy a diesel engine car for their lack of sparkplugs, plug wires and distributor. No gradual loss of efficiency due to fouled plugs.
I'm sure there are many more small things to do, pretty much basic maintenance with some common sense thrown in plus a few you may not have though about.
i remember in one of the mythbusters episodes they tested drafting(wind resistance) on a car and how it affected fuel efficiency. wind resistance does make a big difference. "Going beyond the speculative mathematics of fluid dynamics equations, the Mythbusters demonstrated the principle scientifically in episode #80, confirming the improvements to fuel economy. Using a NASA wind tunnel, the Mythbusters used scale models to demonstrate wind resistance was reduced up to 93% (with a dangerously close simulation of a ten foot following distance). Following the wind tunnel experiment, the Mythbusters hooked a computer directly to the fuel injectors and tailed a truck in a controlled environment, demonstrating gains of 20-40% in fuel efficiency" http://www.omninerd.com/news/Mythbusters_Confirm_Drafting_Improves_Fuel_Economy
Tachometers show us speed
Does your car only have one gear?
Every time I put gas, I calculate the mpg by keeping track of the miles I've gone and how many gallons it took to fill up. Over time, one gets a rough estimate of driving patterns increase efficiency, or when something is wrong. I doubt that have a fuel consumption display in prominent place would help. Even folks that don't pay too much attention to their fuel consumption now that this tank of gas didn't last as long as the others and yet, will not make any changes to their driving habits.
Ha! Who knew penis contest can be useful?! Well, except for that other use. Now that's what I call 'THINKING'.
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
What I've found is there's two sets of best practices, depending on the type of driving.
1. Highway driving, dominated by long periods of cruising. With modern aerodynamics, air resistance isn't usually a problem for passenger cars at posted speed limits (up to 75mph). SUVs and trucks have issues, but if you're interested in fuel economy changing to something else is the single biggest fuel savings you can get. Fuel consumption then's determined by two things: how efficiently your engine's turning fuel into power, and how many RPMs it's making. The first you can find by looking at a graph of your engine's power band (power produced vs. RPM). It's a plateau with a drop-off at either end. You want to stay in the plateau region, if you let the RPMs drop too far or climb too high your engine's burning more fuel than it needs to to generate power to keep you moving. The second's mostly determined by what gear you're in. So you want to maintain the speed that keeps you at the low end of the power band in the highest gear you have available. Any slower than that and you need more throttle (and more fuel burned) to maintain speed, or you have to drop into a lower gear and increase your RPMs (which means burning more fuel).
2. City driving, dominated by acceleration from stops. Speed has a small effect, but the biggest fuel burn you have is accelerating away from a stop light. So adjust your speed to match the interval between lights as closely as possible. If you find lights going green just after you've stopped, slow down a bit. And if you find them going red before you get there, speed up. Going faster may burn more fuel, but starting from a dead stop burns much more so you save by avoiding the stop. And don't lolly-gag on the acceleration. You don't want to peel out, but you want to get up to speed fairly quickly so you spend the least time in lower gears. Remember, the lower the gear the higher the RPMs at a given speed and the more fuel you're burning. Plus, getting up to speed smartly makes it easier to judge the speed you need to maintain to hit the next light while it's green. Spend too much time accelerating and you'll either have to hit a much higher speed or you'll miss the next green, have to stop, and burn all that fuel accelerating again.
...I found details of a contest in the UK you might want to beat. The Peak District, for those not familiar with England, is a mix of gentle, rolling hills and extremely steep inclines. Even walking up from Castleton to the Blue John Caverns is tough going, if you're not a seasoned hill-walker. So, to achieve fuel efficiencies massively above the "national average" (where "average" drivers tend to stick to roads that are flat and relatively uniform in speed) is very impressive. 83 MPG in a Toyota, just by driving better, is not bad at all for the terrain. (The 10,000 MPG specialist fuel-efficiency racing cars can manage on the flat is an unfair comparison.)
As an aside, students will typically drive to/from colleges that are relatively nearby, drive to/from nearby pubs, nearby cinemas, etc. If you could calculate how much fuel a typical student would actually NEED to burn to meet all typical student expectations of where to go, what to see, then you should be able to produce a more-or-less disposable car with plug-and-play gas tanks and oil cartridges. This could be made extremely cheap (far cheaper than a regular car) and free a group of people who live on tight finances anyway from the vagaries of oil prices. Would they buy such a vehicle? Well, depends. If they've been given a Ferrari, no. If they wouldn't otherwise have a car, especially in mass transit/cycle-hostile cities in the US, then they might. Less money on transport = more money for booze, women and clubs.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
I've seen some people do some really stupid things lately, seemingly to save gas.
The other day I'm behind this lady at Burger King, and we were probably about 4 cars back. Every time we moved up, she'd start the car, drive up, and then turn it off.
At first I thought maybe the car was overheating, but then why not just go in? It was still early enough and the dining room was open.
I almost wanted to get out and tell her "You stupid shit head, starting your car squirts an ass load of gas into the cylinders - you've probably used more gas in this line than you would sitting idle for an hour!"
People can be such morons..
The single best way to save gas in any car is to simply drive smoothly - don't accelerate too fast, don't drive over 60-70 on the highway, and try to stay a constant speed while driving. That's it. It's not magic and there's no magic solution.
- It's not the Macs I hate. It's Digg users. -
I hope you don't do that where there is a turning lane. I have lost count of the number of times I have lost my right turn light because some numpty cruises up to the red light and blocks the entrance to the right turn lane.
I found a way to really improve on fuel economy. It's called Public Transportation. Maybe I should patent it! :D
Joke aside, One person driving a car its terribly energy inefficient. Its nonsense to use a 4500-5000 pounds vehicle (avg. car weight) to move a 180-220 pound payload (avg. person weight).
Not quite so good then if it's measuring L/100km I guess.
For the low low price of $289, you can actually turn your mileage into a game courtesy Think Geek.
There are other mechanical and electronic devices that play far too much into both fuel consumption and fuel consumption rate to give accurate catch all advice for every car.
There are many cars with multiple camshafts that operate by forcing fuel into the engine for longer periods of time such as Honda's VTEC and iVTEC, Toyota's VVTL-i and Porsche's VarioCAM Plus.
A system such as that of a current generation Honda iVTEC 4 cylinder would benefit from acceleration until just before engagement of the "performance camshaft" to achieve maximum efficiency.
Two other incredibly complex parts of the fuel efficiency equation are turbochargers and superchargers. Furthermore certain turbo-charging systems employ variable geometry turbochargers which are activated relatively early in the power band.
This question needs to be individually assessed for every car out on the road in whatever condition it may be in.
Insert witty comment here.
Fuel Efficiency is rather quite simple.
Mass is the most important aspect for fuel efficiency when accelerating. Aka "stop and go" traffic in the city. Get a car that weighs less. Accelerating slowly will help a little bit. Try to maintain a constant speed, slowing down and then speeding up again is just wasting your gas by having to re-accelerate all that mass
Aerodynamics is the most important aspect for fuel efficiency once acceleration has been achieved. Thus its the most important for highway travel. There's tons of theories pertaining to aerodynamics. Simplest rule is that any geometric shape will be more aerodynamic if its smaller! Get a smaller car!
Generally a motor is more efficient as it approaches its nominal output. This is slowly canceled out by wind resistance. Where the two meet is the "sweet spot" you want to aim for. Driving either slower or faster will increase fuel consumption per mile. Back during the 1970's energy crisis, some government scientists determined that the average sweet spot was at 50MPH. Modern cars have both moth more efficient motors and are generally more aerodynamic. So the sweet spot is probably a tiny bit higher than that by now.
To recap. Get a small car that weighs less. Accelerate slowly. Maintain constant speed. Going 30MPH in a 45MPH zone will not save on gas in the slightest.
... and in the DRM, bind them.
If you're not willing to give up driving in toto, driving less will do wonders for your gas consumption. Move to a city (of the sort with public transit), buy a bike, and watch your gas and insurance bills tend towards zero.
There's a special circle of heck reserved for slowpoke jerkasses who make me miss lights, especially if they barely make it through the very tail end of the yellow right in front of me.
you mean driving more carefully, maintaining safe distances and control over one's vehicle at all times is not having concern for others?
Install megasquirt'n'spark and hack your own car.
http://bgsoflex.com/megasquirt.html
Not open source, but certainly some degree of community development. (Actual OSS for it would rule)
i am endorsed for the carrying of dangerous goods, please be giving me your depleted uranium
It's like when you are driving a car, if you are driving a car with lots of seats so that you can take your kids to school, you are probably counting Libraries of Congress while using 10-40 oil. But if you use Kerosene instead, and drive a truck instead, you'll make twice as many tri--
-Oh wait-wrong window!-
Want to improve fuel economy? The Mythbusters hath provided the way...... Don't think that this fuel economy doesn't come at the cost of safety, however...
I have no problem with your religion until you decide it's reason to deprive others of the truth.
I've computed my mileage ever since I bought my 2005 Accord. I used to get 27 mpg commuting 25 miles to and from work. The drive is a mix of city streets and rural highway. When gas hit $4/gallon, I backed off from 65-70 miles/hour on the highway to 55 and accelerate more slowly. I also give the car in front of me more leeway so I can maintain a steadier speed. The combination boosted my mileage from 27 to 34.5 mpg. As gas prices fell from their peak of 4.55/gallon, I started speeding back up and at 60 miles/hour, my mileage has dropped back to 32 mpg.
Those are data for one car, one driver.
Automotive post on /. = FAIL
Does everyone drive a dumptruck where you live? Where do you get 4500+ lbs average vehicle weight?
First off, the guy's site only lists data for one car - a Volvo sedan. Secondly, he doesn't mention whether it's an automatic or manual, though I suppose it's an automatic. That makes a huge difference, because what's happening at 35mph or so is that the torque converter is locking up and he's in fourth gear/overdrive. We're talking gearing so tall that 3500rpm or so, where it makes it maximum HP, it would be going somewhere well over 100mph. So 35 vs 55mph hardly makes a difference due to the mile high overdrive gear.
There are different ways to get maximum mpg:
1 - if you have an automatic, it's the exact speed where the torque converter locks up. This usually is in the 1300-1500rpm range for most cars. You want to accelerate as slowly as humanly possible and nudge it up to where the torque converter locks once it hits top gear.(usually about 35mph) Basically lug the engine like crazy and eek along. Time isn't a huge factor since the converter lets you lug the engine like a diesel.
2 - if you have a manual, it's top gear at lowest practical rpms while not lugging the engine or making the clutch slip. This means skipping gears when accelerating most of the time as well. You want to get up to that speed as quickly as possible without making the RPMS go over about 3000(throttle position sensor and egr goes into bypass mode and it just starts dumping more gas since air is already maxxed out) or hitting full throttle.
So you want to accelerate smartly in 2nd and 3rd, then go straight to top gear and back off. You want to go as fast as you can while keeping the fuel to mpg ratio the same while getting there as quickly as possible(since there's no torque converter and you can't lug the engine, there's a spot in top gear where you do a mile the quickest with the least fuel spent.
And it's different for every car. I had a Buick(automatic) that got maximum MPG at exactly 51mph. My 4Runner gets maximum mpg at exactly 67mph(manual transmission).
Is this some curious American-state-of-Oklahoma thing that I am unaware of...?
Using the holy grail of OSes...
The gas prices in your town are going up? In the rest of the U.S. gas prices are going down.
I get a chuckle out of Americans' fuel economy problems- yet they refuse to buy diesel-powered vehicles (half of the new vehicles sold in Europe last year were diesels, including passenger cars). I have a 2006 TDI Jetta that gets 5.25 l/100km (~54mpg for you people living in the past). It gets the same fuel economy regardless of whether I drive 80kph or 130kph. City economy drops to around 6 l/100km, but since I live in a rural area and only drive in a city once a year, it's trivial. The fact that GM won't be selling its new high-efficiency diesel cars in the US because there's 'no market' means that until Americans are willing to invest in better fuel technologies they will be at the bottom of the food chain when it comes to dependence on imported petrochemicals. If I lived in Europe I could purchase a car with even better economy than my Jetta, but for some weird reason (yeah we all know what it is) even in Canada the European autos don't meet 'emissions guidelines'; yet, Volkswagen can't keep its diesels on the lots here, the demand is so high.
"Apparatus dignosco occultus, satis non supernus."
I have a 1993 Escort wagon and I get 36mpg on an unmodified automatic.
My gearhead brother says the motor is designed to run optimally within a range of RPM. It will run better within that range and the load still has a significant impact upon it.
I never go above 2500 rpm; I must do about that on the highway. Whatever gear it runs in, I try to keep the rpm low as possible which likely means that I'm actually ending up around the sweet spot for my 16 year old car (I can hear & feel it changing gears.)
A newer car designed for higher average national speeds (and being newer) likely runs better at a faster speed; that is why some people do better when going 70mph-- they are at the right rpm and gear for the speed. It is still a WASTE because the wind resistance is a CUBIC function and at 55mph you are using about 50% of the power fighting wind resistance (it gets worse as you go faster-- and its not linear, its cubic growth.) So if the car was designed for a better speed (55) then it would get even better millage than it can currently going its design "ideal" of around 70mph.
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I coast as much as I can; I always avoid the brake to save on having to replace them. I do not draft that much because I'm only going 55-60 on the highway due to the fact my rpm reaches 2500 at that speed (everybody passes me.) I slow down on hills (due to rpm.)
If I drive like everybody else, I get about 25mpg and wear my car out quicker. On a long journey, driving fast only gives me about 10-15 min of time but costs me in gas and wear.
I think that 30mph roads are probably ideal because of wind resistance and my gearing causes me to almost idle at that speed on level ground; however, all the stop/starts involved on these roads likely undoes the benefits so I get around the same millage in town.
Fuel injection means on/off only wastes about 10seconds of gas; having just figured this out, I can't say how much turning the car off for >10sec stops will give me. I shall see.
Democracy Now! - uncensored, anti-establishment news
Highway patrol in Seattle have started ticketing people for driving too slowly (hypermilers) and rightfully slow. I wish more cities/municipalities would start doing this, cause it's irritating as hell and completely useless. You get worse mileage the slower you drive. Please drive the posted limit. (It's safer for everyone)
When the guy in front of me is breaking wind I just pass him - It isn't worth the savings to smell it. I only like my own brand!
Great suggestion. When doing that, be very mindful of cars that might run the red. Moving into an intersection at full speed on a fresh green light with another driver racing and failing to beat a red can be a very deadly combination.
You're a little late - have you looked at gas prices recently? I saw $2.79/g today in Austin.
"It is our blasphemy which has made us great, and will sustain us, and which the gods secretly admire in us." - Zelazny
Clutch in the vehicle will need to supply some fuel to keep the engine spinning at minimum revs.
If the clutch was engaged when coasting then the cars momentum could keep the engine turning without requiring any fuel at all.
I'd have thought A vaguely modern car's ECU should be able to drop fuel delivery to zero if you are coasting with the clutch engaged. Why put any fuel in at all if the engine is turning above minimum revs and the driver isn't asking for power with the accelerator?
Boffoonery - downloadable Comedy Benefit for Bletchley Park
I drive a 98 Crown Vic V8 and get 19-21 mpg city and almost 30 mpg highway. You know how I save money? I don't buy brand new hybrids with huge insurance payments.
Now everyone in a pickup or a minivan is busy going 15mph under the speed limit to get a rise out of the 59 cars behind them with someplace better to be than behind their row of stupid stickers. Oh look at me, I discovered a new way to save money, look at me I'm so superior. No you're just an asshole who now has a good reason to drink and drive.
I know it isn't really a behavior, but if you can't afford a hybrid, get a used high efficiency vehicle. It doesn't have to be new to be a gas sipper.
Nissan has a CVT in their Altima but the mileage isn't extremely awesome, not bad at all though. It's supposed to do the "remain in the power band" thing for you if you don't abuse the throttle. You can pretty much stick at the optimal throttle position and it will keep the RPMs almost constant as it accelerates to speed. On a flat surface this RPM/Torque/Speed optimization continues.
Personally, I got a motorcycle. 2008 Suzuki Boulevard M50 (~800cc) costs in the $8k range rolling out the door. Gets 47 MPG City/Highway mix. Haven't had it on the interstate much yet, RPMs aren't optimal at 70MPH though (going by sound, no tach on this model.) Going around 55 on county roads gets it up over 50MPG.
Over the past couple of years I've tracked the mileage I'm getting in my 2000 Corolla pretty closely. I've adopted several techniques that, with practice, have allowed me to boost mileage by about 25%.
1. Avoid using the heat and air conditioning. In the winter I park in the sun and in the summer I park in the shade and use a windshield sun reflector. As a result, the car is never either freezing cold or roasting hot when I get in it. In the winter I have a seat warmer that fits over the regular seat and plugs into the cigarette lighter. Uses very little juice and keeps my butt nice and toasty. I have a 10 minute commute, so it's almost pointless to use the heat or air since by the time the car starts to become comfortable, the trip is already over.
2. Maintain steady speed, accelerate and brake gradually. It takes more energy to change velocity quickly.
3. Maintain momentum. Keep your eyes ahead. If you're headed for a red light, slow down to give it more time to turn green. It takes a lot of energy to accelerate a car from a dead stop, so avoid stopping if possible (and legal).
4. Gravity is your friend. Put the car in neutral and coast.
5. Increase tire pressure. The manual suggests 28 psi, the tire says max pressure is 44 psi and I currently have my tires at 35 psi. The ride is a little rougher, but I can definitely coast for greater distances.
6. Turn off the engine. There are a couple of long lights on my route and I will simply turn the car off as I approach them to avoid having the car idling for a full minute or more. Once you adopt these techniques you learn how fast you have to be going at which points in order to coast for decent distances. On routes I'm very familiar with, I probably have my engine off 15% of the time. I don't turn the engine off at all if I'm not really familiar with where I'm going.
Using these techniques I've boosted my mileage from 34 to 43 MPG. I do not commute on the highway, so my first chance to try some of these techniques on the highway was a trip taken this summer and the results were better than 50 MPG. The car is rated 31/38.
Another change I made was to start working at home one day a week. The numbers work out as follows. I was driving 8000 miles per year (not a lot, I know) and I'm now driving about 7000. I was getting 34 MPG and I'm now getting 43. So I was buying about 235 gallons of gas per year and I'm now buying about 163, which is a 30% decrease. I used to fill up every 2 weeks. Now I fill up every 3 weeks. Each individual thing doesn't make a big difference, but when you put it all together, the difference is significant.
DD
"Can I finish? Can I finish?
We should all be driving Hummers at 90 mph. Burn all the oil up faster, then the US gov't can pull it's collective head out of it's backside and adopt a sensible middle-east policy.
The Russians have won. They have made the world a cesspool of distrust, greed, fear and hate.
"a SUV comes up behind you while you're coasting, honks, pulls around you and speeds ahead only to stop at the light, and then you smoke him as you coast through the light just as it turns green."
Yeh, I call it the "tortoise and the Hare" race. Sometimes it can go on for several changes of traffic lights, and annoys the crap out of the other driver! HEHE
The throwout bearing is also known as the Jesus bearing to those who wrench on cars. Usually after rebuilding the engine, installing it in the car, and topping up the fluids, you'll notice the Jesus bearing sitting on top of the toolbox.
i don't think driving slower than the limit will really save you fuel, however what i feel will save you fuel is accelerating slower. most gas is burned when joe jackass needs to be at the limit (and beyond) in 3 seconds or less at takeoff. this could account for the illusion that people are driving 'slower.'
i've modified my habits to take it a bit easier on the accelerator. also because after 3-4 speeding tickets, you tend to want to avoid them. sometimes an impatient person will try to zip around me because i'm not accelerating fast enough for them.
Actually, not so much. I drive a Toyota Prius as a work vehicle, and after the first couple weeks of "ooh, let's see how ubergood I can get", you ignore it and drive it like a regular car.
I have a very heavy foot, and get about 41mpg (mixed city/highway). My coworker with another fleet Prius drives very nicely, and gets about 44mpg.
My wife drives a Honda Civic, and gets about 33mpg (we work in the same office). Assuming a Prius at $25,000 MSRP, and a Civic at $22,000 MSRP, it's gonna take a LONG time to pay off $3,000 for a ~10mpg difference.
I have an 2001 Sentra and just inst hooked up a gadget I got from Think Geek (ScanTool, I believe its called) that reads the engine computer through the OBDC2 connector. I can verify that taking my foot off the gas does shut off the injectors if the car is in gear and going fast enough. From the ScanTool manual I infer that this behavior is common, but not universal among cars.
Dropping my speed from 75 to 70 has gotten me about another 3 mpg on a 40 mile commute and essentially added about 2 minutes to the trip. Finding areas to strategically put the car into neutral (i.e., going downhill) has netted me about another 1 mpg. I have tried driving at 65, but it added another 4 minutes to the trip and only about 1 mpg more so that wasn't worth it. Also, speeds of 65 and less are really hazardous in most places... the only time anybody does the speed limit where I live is if a cop is on the road. Hypermiling works, but I am careful about it. I don't turn the engine off, or coast in high traffic where I will clog things up and aggravate people. I think one of the other things that has helped is cutting out the hard accelerating and braking. I now accelerate moderately to enter the highway and keep the high speed passing to a minimum. I also coast around town as much as I can, if it is safe.
sweet spot with my 06 Diesel at 65mph. On cruise control with 6 people, 5 dogs and 3/4 of a ton of camping gear (no joke) I get 18mpg. I got 19-20 before this new low sulfur fuel. I guess its the resistance / miles traveled / torque all finding their respective happy places.
Si vis pacem, para bellum! For evil to succeed good men need only do nothing!
Can someone explain it using a car analogy?
Oh, for mod points. Most people (well, most men anyway) are competitive, and we like to beat our "high scores". Tachometers show us speed, clocks show us time, but neither of those contributes to efficiency. Adding a fuel economy display gives a better goal to beat.
This is why I log my mileage and how many gallons of fuel I refill every time I go to the gas station. Sure, it's not instant, but it does tell me my average for when all I do with my car is drive to work and back. Depending on whether I'm being aggressive or not, my car gets between 29-32 overall (although that's mostly freeway driving.) Lately I've been staying in the right lane and doing an average of 60mph whilst nearly everyone else is going 70+
The biggest problem I see on the roads are large cars being driven around with only 1 person in them! How "fuel efficient" is that?
About 9 months ago I got sick of paying high prices for petrol and wanted to do my bit for the environment, so I got my motorbike license and purchased a 125cc scooter. I haven't looked back. Now my wife and I only have two vehicles, a small 2.0 litre car and a 125cc scooter. These two vehicles are fine for everything we need them for.
While I admit scooters aren't right for everybody, they are definitely a possibility for the majority of people. When I try and encourage other people to do their bit and buy a scooter they often come back with the following responses...
"They don't work out that much cheaper once you buy everything." - Complete BS, sure there's a little bit involved in the outlay (Scooter AUD$3000, license/training AUD$500, gear AUD$500, rego AUD$350, comp. insurance AUD$200) but once you're up and running these things run on the whiff of an oily rag. Consider it an investment. Right now I'm doing about 150km per week to and from work (and a little bit of running around on the weekends), I'm averaging about 30km per litre! It costs me around AUD$9 per week to fill up, that's with 98RON premium mind you! So you do the sums and see how much it will save you.
"Scooters are dangerous, you could get killed." - Again, complete BS. I was sceptical about how everyone kept saying how dangerous riding a scooter would be. So I did my research and contacted my state's Transport Authority. The stats were even surprising to a sceptic. In the past four years in my state there's been one fatality on a scooter and only three other fatalities on motorcycles less than 250cc. Once you go over 250cc, people seem to become retards and there are a lot more deaths. Mind you, 2/3 of those were with stationary objects i.e. poles, parked cars etc. People forget too that on a scooter you're a much smaller target and much more agile. The main risk I've faced seems to be people coming into my lane without checking blind spots. In all cases I've been able to successfully swerve/break/accelerate out of the way.
"What about riding in the rain, you'll get wet." - No, you don't if you have the right gear. I bought a weatherproof clothing straight up. I wear this gear over my normal business attire with leather shoes and I'm yet to get wet. I've even ridden in hail and I didn't feel a thing!
"You can't carry much stuff on them." - This is the only place where scooters fall down slightly. But still, scooters offer a few storage options. Most come with storage under the seats - big enough for a bag or your helmet. There's usually a bag hook to hang some shopping bags, you can get a top box put on the back for more storage and I also wear a back pack.
"They're too slow and therefore dangerous." - This is true for the 50cc scooters, which I believe are only suitable for inner city riding. But my 125cc will top out at about 100km/h and will happily cruise at about 90km/h. They are also *very* quick off the line.
Did I also mention they're very FUN to ride?
So what's your excuse?
The logic is that the majority of people are going to drive at a certain speed on any given road regardless (the "85th percentile" rule) and the one doofus going significantly slower than this becomes a very unexpected, slow-moving obstacle which requires people to either hit the anchors suddenly, or attempt to swerve around, both of which are clearly unsafe behaviors.
While most cops won't care about this excuse because they want to maintain a ticket quota, many judges will, assuming no other violation and a good attitude, accept the "I was just keeping up with traffic" line as grounds for dismissal or reduction of a citation. There's a reason for this.
I grant you that this study, and some others like it, mention only accidents and do not discuss or even mention fatalities, but the reduction of total accidents when everyone drives at the 85th percentile is a pretty clear fact. If everyone drove slower this probably wouldn't be the case, but since we aren't going to change the rset of humanity's driving patterns, telling people to drive slower than they should is dubious advice.
mirrorshades radio -- darkwave, industrial, futurepop, ebm.
I'm too lazy to read the entire 400 comments, but how about focusing on reducing curb weight? 1/4 tank covers a lot of distance in my mighty Corolla, and I know it may lend to the inconvenience of stopping for gas more than once, but I'm schlepping a good 40 to 50 litres of liquid ballast around for the better part of a week for nothing. Surely the energy saved from not hauling that everywhere adds up over time?
While I'm sure it's more efficient to drive at an average of 60mph than, say, 80mph, isn't the amount of gas consumption ultimately dictated by the RPM's?
I do a lot of city driving and it's not likely I'll I reach 60mph anyway. That said I admit that I tend to do a lot of "jackrabbit" starts, and get the rpm's up to 6000 while accelerating after a green light. Is there much benefit to keeping my rpm's under 3000 in this scenario or is the fuel savings negligible?
If you're driving slowly to save yourself some money, you'd better get the hell out of my way because my time is worth more than a fucking gallon of gas.
Sig this!
Its how fast you go fast.
Braking and accelerating hard both waste fuel.
Everytime you brake, you are turning speed (that you used fuel to attain) into heat.
If you accelerate hard and get up to speed, only to reach the next light before it turns green, then you just wasted all that gas. They key is to accelerate slowly, and try to arrive at each light when its green.
Stop signs of course you have to stop for - but do you want to rush right up, and be the third car in line, and have to go, and stop, and go, and stop over and over? No, slow down, and leave enough space ahead of you so that when you reach the stop sign, the car ahead of you has already gone through, so you only have to stop once.
(Oh, and a side effect of leaving plenty of space between you and the car ahead of you, if they have to slow or stop suddenly, you are less likely to become a resident of their trunk. Not to mention the costs for the ticket you'll get, as well as increased premiums after your insurance pays for their damages)
For more in-depth info about getting better gas mileage, see http://www.avoidgaspain.com/ (Disclaimer: I am a relative of the author of that site)
I'd like it to be an external display, too. You line up next to that other car at the light, give the other driver the evil eye, and when it turns green, you both creep out of the intersection. Who won this, the world's most pathetic drag race? Check the readout.
I actually took an upper division Physics course called "Physics of Energy Conversion and Usage". About half the class was on fuel economy in cars. Here's what it all comes down to:
City Mileage:
What matters most is how light the car is. You're stopping and starting all the time, so you're re-accelerating all that mass each time you start and then dissipating it as heat in the brakes when you stop (unless you have regenerative braking, which still isn't all the efficient). The second most important thing is how much energy you waste while idling. A big displacement engine needs more gas just to sit there at idle than a small one does (of course, this doesn't matter if the engine shuts off automatically at a stop like in a hybrid). Aerodynamics don't matter around town as wind drag is small compared to rolling resistance and overcoming the inertia each time you leave a light.
So, a light car with a small engine gets good mileage around town.
Highway Mileage:
Here what matters most is aerodynamics, wind drag goes as about the square of the speed and rolling resistance only scales up pretty much linearly. Once you're up to cruise speed, it doesn't matter if you weigh 1,000lbs or 10,000lbs -- you already have the car up to speed so weight no longer matters. The most efficient speed will depend on the aerodynamics of the car. A brick shaped car will have its aerodynamic drag dominate the rest of the equation at a much lower speed than a slick shaped one will.
The factors that go into wind resistance are:
1) cross sectional area, this scales linearly. Double the cross sectional are and you double the wind drag.
2) drag coefficient, this is basically how slick the car is (spoilers in the right places etc.) Note that you can tune this to work best at a certain speed, if you want. That is, you can make the car most "slick" at 55 or 65 or 75 by design.
3) speed -- for the speeds we're talking about, the drag goes pretty much as the square of the speed (it goes way up as you approach the speed of sound, for example), but basically as you double the speed you quadruple the wind drag.
So, a small car (cross sectional area) with good aerodynamics gets good mileage on the highway.
One more thing that matters to both city and highway mileage is what % of the time your car can run at wide open throttle (WOT). Engines are most efficient at converting fuel to energy at WOT, any throttle setting lower than wide open causes the engine to suffer a lot of inefficiencies, mostly in the intake manifold -- the car is sucking air/fuel in through a straw and putting a lot of energy into doing so. It's like a backwards turbo charger. So, what you want is a weak engine that can run at wide open throttle at your highway cruise speed and off the line around town (and then shut it off when you stop). This means, however, that your car is going to suck performance wise and why econo-boxes suck to drive -- the engine has to be *just* strong enough to get the car off the line w/o holding up traffic and able to get it to highway speed but no faster (no passing, unless you're going downhill).
So, what is the most efficient speed for highway mileage? IT DEPENDS ON THE CAR. Of all the variables above, the only ones that vary as speed does are:
1) the aerodynamics of the car: for what speed did the car designers optimize the aerodynamics?
2) the size of the engine: the more powerful the engine the more likely it is to have its efficiency peak at a higher speed because you're closer to running it at WOT (will still get worse mileage at any speed than a less powerful engine, mind you).
I've done enough physics homework to not give a crap about how light my car is. I want a heavy car so when the Ford F250 running late to a job site blows the light and comes through my passenger door I have something to contribute to my half of the momentum-transfer equation, and enough body rigidity and safety features to keep me intact (both of which add to the weight).
My favorite quote doesn't fit into 120 characters. Now no one will like me.
Please don't do this if there are cars behind you. Especially in the left lane. I hate when bozos glide slowly to the light, not noticing the line of cars behind them trying to get to the left turn lane before the light turns.
The problem is this: in most cities I've been in, the lights are timed in such a way that if you do accelerate slowly, (and/or do the speed limit), you will catch more lights. Seems to me that 5 minutes of traffic lights is more consumptive of fuel than 10-20 seconds of moderate accelerating.
I have 1991 Toyota MR2 - no turbo - barely computerized - manual transmission.
Before - I drove without thinking about economy, probably gassin' it too hard on acceleration - drivin' too fast, etc. On a 40 litre tank I got about 500km. that's 8litres/100km or 29.5 mpg.
Now - I short shift to cruising speed. Drive the speed limit and yes I will coast in neutral from time to time. On the same 40 litre tank I'm getting 630km. that's 6.3 l/100km or 37.3 mpg
Just sayin'
The rotational speed of your engine isn't a speed?
I was going to post almost the same information. I was surprised another car also receives the best fuel economy at 85mph; most cars seem to like less than 60mph. Then I found your post mentioning you have a '00 TransAm WS6. My numbers are from a '99 TransAm and an '02 TransAm WS6; both 6-speed manuals. (I upgraded because they were being discontinued.) Like yours, 85mph is best; over 90mph starts eating fuel, and under 80mph loses at least 2mpg. My WS6 has never beaten 24mpg. The '99 reached 26mpg going downhill south from Harrisburg, PA to Charlotte, NC for over 400 miles without refilling -- cruise control and standing on the clutch to slow entering town areas with lower speed limits.
It is because our cars are cooler. The low drag is because we are not driving a block on wheels. The V8 engine and 6-speed transmission allow us to accelerate well and coast without going over 2000rpm.
Do you get better mpg because the West Coast is flatter? In the Philadelphia area, we rarely see a half-mile of road because a hill blocks the view.
In 2007, I did little highway driving and averaged 16mpg, never 280 miles between refills. In 2006, I almost reached 23mpg for a few tanks, but still only averaged 17.5mpg for the year. TransAms are not good if you care about fuel economy. [I don't. The '99 was traded after 3.5 years with 54K miles -- much driving for well-paid consulting work. The '02 is 6.5 years old and just passed 50K miles -- much working from home. I still enjoy all-day pleasure drives.]
I spend my life entertaining my brain.
I bought a little computer called a ScanGuage (check with Dr Google for web sites) that measures fuel consumption and a whole host of other variables. I found my car gets absolutely worst mileage between 0 and 30 mph. The best mileage I get is around 55, which is kind of what a lot of average cars do. There's a balance you have to strike in city driving.
Punching it off the light drops my mileage down to 3-4 MPG for the duration of the burst. If I accelerate a little less quickly, I can get no lower than 10 MPG. The catch is mileage is horrible under 25 anyway, so the quicker you can get your car past that speed the better, but punching it in time to brake for the next light is probably pretty silly too.
Overall the best way to get better mileage is to adjust your speed to minimize the times you have to accelerate and decelerate. IE if you know a red light up ahead is going to change soon, slow down a bit so that by the time you get to the light it will be green. This can save a lot of fuel because you have to spend less energy accelerating.
Also, I've found that the smoother you're driving, the better mileage you get. While accelerating, shift smoothly, rather than the bursts of acceleration that most folks do. In fact, a passenger can't even tell you shifted (or the car shifted), mileage improves.
Also when on cruise control, be more proactive around hills. Disengage the cruise early and accelerate some so that your momentum can better carry you over the hill. Don't wait for the car to down-shift. Let the car slow down some so that down-shifting isn't necessary. On the other side of the hill, gently accelerate to the speed you want to cruise at before turning cruise back on as cruise tends to cause things like down-shifting when accelerating. One other tip when climbing a small hill on cruise control (with an automatic with a locking torque-converter) is to tap the accelerator, which unlocks the torque converter. This will give you a bit more power without resorting to a downshift (you should see your tach rise slightly).
Anyway there are lots of things people can do to drive better and save fuel. Also passengers tend to be more comfortable too, with less motion sickness.
I've noticed this as well.. in particular i've noticed a plateau effect on my hundai.
Each 1k rpm mark will sustain a 10-20 mph range of speed.
Stick to the top of that range and get the most economy.
VLC FOR MAC IS DYING! IF YOU DEVELOP, PLEASE SAVE IT!!
I'm calling "bullsh*t" on almost everyone here.
Okay, geeks: Raise you hands if you've ever opened the hood of your car? Next, who here has ever personally changed the oil in their own car? A tire?
Don't feel bad. This subject has been brought up the in wrong place. It's as if I walked into the service bay of an auto repair establishment and started asking computer-related questions.
Big humorous component....
Who says there are no ladies on /. ?
Everywhere I drive, I drive the posted speed limit.
My Dodge 350 with the Cummings Turbo Diesel gets 20MPG. I drive about 250 miles per week.
My VW Jetta 2.0L Gas engine gets about 30MPG. 400 miles per week.
My Suzuki Samurai gets 17MPG (modified for offroad). 100 miles per month.
My offroad 4x4 rock crawler gets 50MPG with a VW Turbo Diesel. But I don't go over 25MPH in it. 50 miles per month.
My Ford 250 Gasser gets 10MPG. What to buy it? $1000.
The above is not worth reading.
...but how fast you get there.
Driving 35 MPH in a 45 zone won't really increase your efficiency an awful lot
I've made a point (since I was laid-off by HP (Thanks, BTW, I've found a much better job!)) to not allow my vehicle to go above 2000 RPM when accelerating. I've increased my fuel efficiency almost 20%.
It's kind of annoying to accelerate that slowly, but being able to drive an extra 50 miles on a tank when I didn't have a job has been an enormous cost-saver.
My car has a big 4.6L V8. It's a lot of fun, but not terribly effective for good mileage, so I did a little bit of experimenting on what driving style is most efficient.
It varies from car to car, but mine is most efficient between 45 and 55mph.
The most interesting thing I discovered is that ignoring traffic laws approximately returned me a 20% improvement in fuel economy - ignoring stoplights, stopsigns and speed limits. This isn't to say that you should do this recklessly - for example, sometimes when you're at a 4-way intersection and you have good visibility you can safely (but illegally) run a red light or stop sign.
Coming to a full stop is also bad for mileage. You burn more gas every time you accelerate so the less you accelerate, the more efficiently you're using your car.
For the record, I only did this for 1 tank of gas, and I follow the rules when I drive now. This was just an experiment just to see how much following the rules was costing me :)
--
#include <malloc.h>
free(your.mind);
Kinetic energy is your friend. Friction is your enemy.
drag goes up as the square of speed.
power required goes up as the cube.
do the dimensional analysis and you'll find that fuel economy goes down as the inverse square of speed. 120mph is 4 times worse than 60mph.
in the limit this is absolutely true, but at lower speeds there are other factors. mileage in my civic hybrid peaks at about 45 mph (~60 mpg), and i still get 50mpg at 65mph.
YMMV
great.. more leftist sexism
That chart is disinformation, although driving patterns might produce such a skewed result. Old Consumer Reports included mileage charts for each vehicle tested: in five MPH increments. Fuel economy always went down as speed increased - even from 25-30 MPH. The mechanical (friction) load increases in a linear manner, which is not too bad - but the wind resistance increases with the square of velocity, eventually becoming the overriding factor.
for example, an impatient bozo in a SUV comes up behind you while you're coasting, honks,
Ah, you mean the guy the who wants to make the turn light, but he's being stopped by the "coaster". He'll sit at the turn left light for five minutes getting 0mpg waiting for the next green light. Only if he'd bought a hybrid.
Not every body gets in the way doing this, but some people do, it's kind of an annoying and selfish habit in some circumstances.
M0571y H@rml355.
http://www.cleanmpg.com/forums/forumdisplay.php?f=23 has some hints. They also have specific articles for some cars like the Prius. See http://www.cleanmpg.com/forums/showthread.php?t=1224.
http://www.motherjones.com/news/feature/2007/01/king_of_the_hypermilers.html is an article about a hypermiler (Wayne Gerdes) who achieves 59 mpg in his non-hybrid 05 Honda Accord.
Gerdes was part of a team of who set a record (which has been since beaten) of ~110 mpg in a Prius over 1397 miles on a single tank.
There are some other tips at http://www.hypermiling.com/.
a couple of you had it earlier, the best way to drive efficiently is to keep your engine in its torque band, where its making the most torque and functioning the most efficiently.
and maintaining a low engine speed with light throttle is generally a bad idea, your engine runs rich because it needs to keep itself going and you waste more gas.
but if you're considering buying a new car, the best way to save money is not to buy it and keep your current pos until its thoroughly shit itself.
and get good spark plugs to make sure you're getting full combustion.
I've noticed I get less tired if I walk rather than sit.
just be patient. the speed limit is an upper limit. get used to people thinking differently than you, and acting accordingly.
No one can understand the truth until he drinks of coffee's frothy goodness.
--Sheikh Abd-Al-Kadir, 1587
Astonishing that I haven't seen anything about that in the comments (though I haven't read all of it yet): make sure to have appropriate tire pressure can make a huge difference as well.
Go with at least the suggested pressure, maybe even a little (up to 0.5 bar) above and you will notice a difference in fuel consumption too.
Don't get over 0.5 bar more than the suggested pressure because it may effect the tire grip in a bad way.
This will affect your fuel efficiency no matter if you drive fast or slow.
This seemed like an interesting alternative: http://www.poulsenhybrid.com/index.html Other companies already make technically more advanced solutions, but typically for trucks, buses etc.
Steering Lock
From the sounds of it, neither you nor the parent poster have actually performed the above operation you are warning everyone else to avoid.
On most cars, the power steering is hydraulic, and the brake booster is powered by intake manifold vacuum. So long as the car remains in gear, both will continue to operate even with the ignition off. Credat Emptor: Some cars use electrical power steering and brake booster. I'm not sure how these behave with the ignition in the accessory position.
Additionally, the brake booster typically holds enough vacuum for one to three *hard* applications of the brake, and on a typical sedan, power steering is only required when stopped.
Furthermore, the steering column lock does not engage when the engine is turned off. It engages when the key is turned to the steering lock position. The engine off position is the click just before the engine turns on. Typically, this is where your radio works, but the car doesn't run. Most modern automatics prevent the key from being removed unless the car is in park. Most manual transmissions require a button be pressed, or the key manipulated in a special way to prevent the steering lock from being accidentally engaged. Again, so long as the car is not inneutral, you should be fine.
So, is this technique safe? Hard to say. I've personally done and experienced everything I've written about. I doubt the parent and grandparent poster can do the same. Safe? Probably not... But this is slashdot. We are geeks... Let's attempt to be technically accurate.
It's totally true! Although I normally try and drive semi-efficiently and not push the car too much, the fact is that I'm often in a rush and will accelerate fast to get in front of other cars, etc. etc. But with my new prius with a fuel economy display I'm always driving nice and easily trying to up that mileage rating! Every time the average for the whole trip goes up I'm very proud. :)
You're right, but the principle applies equally to modern EFI systems. Internal combustion engines are more efficient at full load because power output is increased proportionally more than losses are. (Losses are largely dependent on engine speed rather than the amount of torque being produced.) Combustion efficiency itself also benefits at full load from increased dynamic compression ratio, better mixing of fuel with air, and a decreased surface area to mass ratio (better thermodynamic efficiency).
The test conducted by BMW that I'm familiar with used a 528i as the test vehicle (circa 1980). This is a 2.8l straight-six with EFI. They acclerated the vehicle to a set speed, cruised for a bit and then stopped after a set distance. Four variations were mentioned: (listed from most efficient to least efficient according to BMW's results)
throttle 75% open, up-shifts at 2000RPM
throttle 75% open, up-shifts at 5000RPM
throttle 25% open, up-shifts at 2000RPM
throttle 25% open, up-shifts at 5000RPM
So the recommendation is not to accelerate as quickly as possible, but to keep the engine operating near full load at low RPMs. Note that using 75% throttle rather than 100% is specifically to avoid having the fuel injection switch to a richer mixture as it does at WOT.
At this time BMW was working on the 528e. Since the straight-six runs nice and smooth at low RPMs as it is, they designed one that with a shorter camshaft duration and higher intake air speed for greater low-end torque. They also used taller gearing. IIRC they were able to achieve 40mpg at 37mph in top gear. Although this came at the cost of reduced peak power output. Modern tech like variable valve timing/lift and variable length intakes are aimed at getting the best of both worlds.
It's perfectly easy to flip back and forth between neutral and drive in most automatic transmissions; I coast down hills in neutral all the time.
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
On the other hand I know a few people with a fuel economy display in their car that were competing to have THE LOWEST fuel efficiency last time we were all out driving together... These things don't always work out the way it seems at first glance.
How about a car that runs on water to save the bills. Maybe even the world.
http://www.reuters.com/news/video?videoId=84561
The new Hummer?
Or maybe the people who take "Drive defensively! Buy a tank!" seriously.
upon the advice of my lawyer, i have no sig at this time
Although demand for gas is relatively inelastic compared to a lot of other retail products (other than basic groceries, I suppose), it certainly isn't perfectly inelastic. Total US demand has dropped 2-4% over last year due largely to the increase in gas prices, compared to a usual year-on-year increase of about 2%, for about a 4-6% relative demand reduction due to price increases.
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
Having recently ditched our fuel eating Saab 95 estate (automatic) that averaged 22-25mpg, we've now got a Saab 93 Sportwagon diesel (dreadful name, but nice car)
We've been testing it's mpg a lot recently. Town driving it gets 35-40mpg depending on conditions and traffic. This at speed averaging around 30mph. On Motorways at 70mph, consumption is about 40-42mpg.. at 60mph we easily get 51-53mpg.
The economy savings between 70 and 60mph are quite considerable. At £1.20 a litre (for diesel) that makes quite a difference on a long journey.
I always believed that cars optimum fuel economy had gotten better at higher speeds, but that's clearly not the case in my Saab.
it might be a Vauxhall/Opel Vectra underneath, but it's still a nice car to drive!
If you are going to coast to the lights, please remember to be considerate of other drivers and not block turning lanes, etc that are not synced to the light you are stopping for. Nothing is more annoying then missing a turn single at a slow changing intersection, because someone selfishly blocked the lane leading to the turning lane by slowing down a large distance from the lights.
Simple rules to follow for good mileage:
1. Drive at the slow end of your top gear (in european cars, this might be about 50mph/80kph in 5th gear) - but no lower... if you are pressing the accelerator and nothing is happening, you should be in a lower gear, or you shouldn't be pressing the accelerator.
2. Drive so that you don't need the brakes very much. Each time you touch the brakes, you are dumping good forward energy as heat energy in the brakes. So: keep some distance in heavy traffic, coast up to red lights, bends and stop signs.
3. Avoid heavy acceleration (but don't accelerate extremely slowly either, you want to get into that efficient top gear, unless you have a curve or stop sign ahead). Do you really need to overtake that car?
4. Keep your tyres inflated, your engine well oiled, and fix any engine problems that occur.
Apart from these, you can save a lot of gas by avoiding unnecessary trips, cycling, taking the bus/train.
he can average 50MPG if he's careful with it, in a 10 y.o. saturn.
Wow.... clearly SEGA should have moved into the automobile industry.
My wife hates me and my EPG gauge. I play it exactly like a game, and If I'm trying to beat a high score (currently 29.7) in a car designed for 20-22. She really hates it if we drive behind a truck for twenty miles.
I find hyper-milers annoying as they cause me to use more fuel from the traffic congestion they cause. They just become obstacles on the highway causing people to break, change lanes, speed back up or causing the whole column of traffic to stop all together. They rarely look at the chaos they create behind them.
*It's not what you can do for the Dark Side but what the Dark Side can do for you!*
A couple of years ago jeremy clarkson did just this test. He found the following... Low rpm http://www.autobloggreen.com/2007/12/26/video-london-to-edinburgh-and-back-on-one-tank-of-diesel-in-an/ enjoy!
I recently tested out a handful of "increase fuel efficiency" techniques.
The first one I tried was "drive slow". This was on the highway in the Midwest, where the road is literally straight for hundreds of miles, and the wind often travels West to East at around 10-30mph. I took the "going there" (Eastward) leg of the trip at 55mph with cruise control. I took the trip back at 78mph (into the wind). The round trip is about 700 miles; one-way 350.
Long of the short of it: the return trip took about two more gallons of gas. not even close to worth the agitation/fatigue of the longer trip there.
(Caveat: there was one less person in the vehicle for the return trip - that'd be 1 less 150lb person, for a total of four on the first leg and 3 on the return).
What I've seen prove the best results, in terms of driving style, is to accelerate slowly. Don't stomp the accelerator. Glide into red lights (ie don't stop right when you get to the light; just let off the gas and break slowly if you see a red light ahead). Yes, it slows overall driving speed, but I still go at (or above :P) the speed limit, and I'd wager in-town driving gets a 10-20% boost in efficiency. Though, this is difficult to do in traffic of any sort, obviously. I imagine it'd be all but impossible in populated coastal areas.
Something else I've seen prove (substantially) successful results are the "HHO" hydrogen augmenters. You'll spend about $15-20 for the parts and spend an afternoon tinkering with them and finding the proper place in your vehicle for mounting (if you're technically inclined), but I've seen some astounding results - 30-50% fuel economy increase, with (in some vehicles) better horsepower. Took my Ford Focus (2000) from about 27mpg to 35-40mpg average.
Rant: Personally, I can't help but think that automotive makers are intentionally not providing our vehicles with the innovations necessary to get better fuel economy (and this is exasperated by government emission regulation which monitors fuel emissions by the gallon not mile). I think they know how to get high-efficiency vehicles which don't suck, even without using hybrid/augmentation technologies. We had cars in the 1980s which got 30, 35mpg. My Focus only gets 27 or so, stock - which is only about 7mpg better than my neighbor's V8 Dodge work van, which is full to the brim with tools and supplies. With hybrid technology, we're only just barely getting what we used to get out of our vehicles.
Yes, I realize that our vehicles are now (mostly) much more reliable than they were 20 years ago, and that they've made a lot of compromises in things like fuel economy to get there. (Or, at least, so the story goes.) Just the same, there are a lot of easy, cheap ways to improve fuel economy (at the very least, on-demand HHO) which the automotive industry isn't implementing - and I have to wonder: why, if a guy unfamiliar with cars can pull 30% better fuel mileage out of his car in an afternoon with $20, why can't automotive manufacturers?
~/ssh slashdot.org ssh: connect to host slashdot.org port 22: too many beers
I noticed that at sane angular velocity there is a peek in efficiency when the turbo kicks in. However, if you go all the way down and let the engine run stationary in fifth gear you can get to a much higher efficiency. I managed to get twice the specified efficiency. The car will be running around 12.5 m/s then (which is about 25 knots)
What happens is that because of the low drag at that speed, the momentum of the car is enough to keep the engine turning above the fuel injection threshold without help. Then the computer decides to stop fuel injection. The result is that the cylinders fire only once in four roughly. Almost any diesel car should be able to do this, as they put way to heavy engines in them.
It won't surprise you to read, that you shouldn't tell your dealer, nor try this on the highway (they have a lower speed limit too).
Please don't ask for help converting this to nautical miles per pint.
Show a man some news, distract him for an hour. Show a man some mod points, distract him for the rest of his life.
It's not in the speed you drive, it's in the way you drive. It's in little things like:
- Don't rev the engine above 2500 rpm, change gears faster.
- When a traffic light ahead is red, take your foot from the accelerator. Modern engines use no (that's right: NO) fuel on engine braking.
- Anticipate to the traffic ahead, e.g. give room for somebody so you can slide into his spot.
- Don't start the engine until you are ready to set off.
And this will absolutely NOT make you drive any slower, but I've seen tests where they showed you could save somewhere in the range of 6 to 15% fuel.
Here's a nice link to a Dutch programme called "the new drive":
http://www.hetnieuwerijden.nl/english.html
SO many car analogy possibilities! My head esplode!
IIRC the old 'jelly mould' Saabs of the 1960s (and many of the later ones) are designed to coast in neutral.
The freewheel automatically disengages the clutch when you take your foot off the accelerator pedal, like that on a bicycle. It was a feature originally something to do with lubricating the 2-stroke engines fitted in the earliest models, not a bug or poor driving technique.
A friend of mine who used to live near Whitby, Yorkshire (which has its fair share of hills) found it rather alarming at first, but got used to it.
Coasting is not efficient stopping. If you just release gas and let your engine brake for you, the forward motion of the car will be enough to keep the engine turning. In other words, the car is usually smart enough to cut the fual to the engine, making you run at zero.
However, if you 'coast', the engine needs fuel to keep turning. So in fact, you're using more fuel. Worst is of course, keeping your speed until the very end.
Just check the usage display on your board computer. If you engine brake, it'll cut to zero.
If you've never been to Oklahoma then you are a luckier person than I am.
I know that my car manual tells me that the most fuel efficient speed is in my car - 57mph. It varies from car to car, although (I'm told) more cars are around this figure.
Having a 6th gear would help, of course. Driving a manual (properly!) instead of an automatic is better again. Engine size is a big factor (and US engine sizes tend to be much larger then European engine sizes). The type of fuel used is another factor (here, we only get 95 octane - we don't get the 85octane 'water' that it used in the US).
The car manufacturor would have taken everything into account to give the optimal fuel efficiency. So check the manual.
Driving slow definately does not help fuel efficiency! However, accelerating hard to up to certain speed causes your car to just drink fuel! Accelerate at a lower rate, and change gear at the right point (between 1800 and 2000 rpm on my car). Drive in the highest gear you can for the speed you are going, and never, ever, floor the throttle!
T.
that weights less. Get a motorcycle, duh.
I've measured my SUV's highway gas mileage at about 24 mpg at 55 mph and about 17 mpg at 70 mph. My sedan, which is more aerodynamic, does not have such a drastic change, but the difference is noticeable.
In regards to the time factor that the previous poster discusses, we're talking about "miles per gallon." This is the amount of fuel it takes to travel a certain distance, regardless of how long it takes you to get there.
Driving about 55 saves a significant amount of gas.
http://www.rd.com/your-america-inspiring-people-and-stories/ease-on-down-the-road/article55921.html There are a lot of tips on how to save mileage there... some of which are discussed in the comments of this slashdot story.
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
Mr. Smythe (first post) makes good points. Combustion engines in vehicles have their engine timing set for optimal fuel consumption by engine speed (rpms). You can be in most any gear so long as you hit that "sweet spot" of engine efficiency and be getting the optimal mpg available FOR THAT GEAR. Many of the vehicles that are being driven just around town, to & from for groceries & shopping & Work, are geared and timed for interstate performance, killing their City driving mpg.
The majority of fuel consumption is expended getting a car's Mass up to speed, in the lower gears. My old clunker has a 302. I just put some new plugs & wires on it and it's got power to spare. However, it stays in 1st and 2nd gear longer due to the tire circumference (225xR14) so I'm going to put a smaller diameter (and circumference) tire on soon, giving => higher revolutions per mile => effectively increasing the engine torque to the ground. In other words, instead of changing the ignition timing for earlier firing I'm changing it -effectively- at the rear tires. I expect it to pull off from a stop or light with much less Workload on the engine (much less gas pedal). It will likely be in top gear (3rd) by the time it gets up to 22 mph and in a "sweet spot" range for optimal fuel consumption in the 22-45 mph range, perfect for my driving. I will keep it off the interstates. That's what our other car is for. I also expect this will enable me to back off the fuel screw on the carburetor...
Industrial Age 2 + How-to Stop Malignant Cancers.
I have a Charger R/T with a Hemi. Typical city driving I get about 16 with it, but if I can get on the highway for an entire tank, I will get about 26 ish, which is allowing for a cruise speed of about 80 on Fla highways. Mine is an '06, and as I understand it mileage has only increased with improvements to the computers.
Transitions in and out of MDS is seemless and not noticeable. However, that said, My car has a hard time with idling. I dont know if it's a symptom of the breed or just mine needing a tuneup.
Allpar.com has a very nice write up on all things Hemi.
http://www.allpar.com/mopar/new-mopar-hemi.html
Drive RPM not mph, most non-turbo charged 4 cylinders operate most efficiently at ~1800-2200 rpm. If you can go 75 mph or 50 mph at 2000 rpm the extra drag at the higher speed is not going to get in the way of fuel efficiency for most cars. What kills mileage is going through the gearing making the engine shift at 3000-4000 rpm back to 2000rpm again and again. So when you get to your sweet rpm at the highest gear on the highway try not to keep accelerating and in the city be mindful of how fast you can really go between lights and try not to get into a higher gear than you need to go another block.
An Education is the Font of All Liberty
25 in a 40 zone down a 4 lane road?
I can't find an online link to it, but there is according to Gary Larson, of Far Side comic fame, there is a special circle of hell reserved for "People who drive slow in the fast lane" next to muderers, rapist etc.
One of the all time funny Far Side cartoons, I have it hanging on my wall in my workshop at home.
This post brought to you by your friendly neighborhood MBA.
Every description of hypermiling I've ever seen describes extremely dangerous driving habits. Just to get another 0.01 of a mpg, these people endanger their own lives and the lives of others through, frankly, crazy driving techniques.
Call a tow truck to yake your car back up the hill.
FRA: STFU GTFO
But none of the comments I've read in here have touched on the comment about the gas gouging.
Improving fuel economy is great. It reduces our dependence on foreign oil, reduces the need to destroy natural habitat to get new sources of oil, and reduces the pollutants that are affecting our environments.
HOWEVER!
Most of the "improve fuel economy" stuff listed here is an effort to reduce the actual cost to the consumer.
How about, while we try to make rolling bricks more aerodynamic, we also start going after those companies that are intentionally inflating the cost of fuel?
For example:
Delta Sonic in one part of Rochester, NY, is selling regular gas for $3.34/gallon.
The same company, about 10 minutes north (but still in the greater Rochester area) is selling for $3.75.
What's the deal here? chances are, both stations are being supplied from the same truck, are owned by the same company (so they are supplied from the same wholesaler), why a 30cent difference in price over maybe 10 miles distance?
Or, why is every gas station in an area the same price? Wouldn't someone able to undercut by 5cents be able to sell a LOT more fuel?
I'd like to see some legitimate investigation into how the cost of gas is set in general, and how the different regions affect it. Preferably something more than the recent Senate BS that was basically a chance for their corporate sponsors to say "we aren't the cause".
This tactic can be quite entertaining if, for example, an impatient bozo in a SUV comes up behind you while you're coasting, honks, pulls around you and speeds ahead only to stop at the light, and then you smoke him as you coast through the light just as it turns green.
Yes! I'm glad I'm not the only person who finds that entertaining. Even if it were a ferrari, if it's at a standing start and I'm doing 20 when the light goes green (if you drive the same route a lot you get a good sense of the phasing), he'll be eating my dust.
You thought you could break the laws of physics without paying the PRICE?
Comment removed based on user account deletion
All of your concerns are addressed in Improve MPG: The Factors Affecting Fuel Efficiency which was Slashdotted more than two years ago.
In a nutshell, yes, the horsepower requirements increase with added speed as your engine must fight with increased drag. So driving slower mitigates the energy required to overcome the additional force.
HOWEVER, going too slow and you don't cover enough distance for the amount of gas you use. In an extreme example, idling at 0mph is an asymptotic point on the mpg graph. All cars have different "sweet spots" where they are optimal. Those "sweet spots" are typically dictated by particular RPM ranges and the corresponding speeds by which a chosen gear will drive the car within those RPM ranges.
Some people will say that simply driving in the highest gear at the lowest speed will always produce the best mpg. Not necessarily so (though generally so). As an example, a 2006 Jeep Wrangler turning 35" tires gets exactly the same mpg in 6th gear as it does in 5th gear at 75mph. This is counter-intuitive but one must remember there are more factors at play within the engine computer than simply RPMs. Looking deeper at the situation reveals that while 5th gear requires more RPMs, the ignition timing is advanced nearly 20 degrees on 6th gear plus the higher RPMs are actually in the engine's torque zone meaning it requires less air (and hence less gas based on the stoichiometric ratio) to produce the same amount of power.
When you understand your disbelief in other gods, then you will understand my disbelief in yours.
Engine designers attempt to limit this as much as possible with something called a "windage plate", but, for over-the-road cars, it's a bit of a compromise. There are height constraints on the engine, so the oil pan can be only so large, and drivers don't want to be messing with their oil on a regular basis, so efficiency loses out a little bit when they pick a "top" oil level. Try not filling you oil up to that level. Your car will run fine with the level at the "low" marker on your dipstick and you can reduce windage a bit, which should increase mileage.
You'll need to check your oil level on a regular basis, and, of course, there's no advantage in a dry-sump engine - but I don't think any current autos have those.
While I'm on reducing internal resistance, think about using a lower weight oil, that will keep viscosity at high temps. Both Mobil One and Amsoil are good at this.
The notion here is that another point of resistance in your engine is the oil in your main bearings. These are "plain" bearings, which are actually "oil wave" bearings in that the crank actually rests on a hydrostatic wave. You don't need more viscosity for this than the viscosity of the spec'ed oil at max temp. Better to get an oil that starts out pretty close to this viscosity and then stays there.
Oh - and nobody's mentioned cleaning injectors. Yes, they clog, and they don't all clog at the same rate, so you end up with some cylinders running richer than the others. Not good for max power - or efficiency. Cheap partial fix: start using Techron. Complete fix: take 'em out and send to a specialist shop (note: talk to folks about specialist shop about Techron - all the ones I've spoke with use it). If you're driving a sportscar, there'll be higher flowing injectors available. Interesting for this discussion as you can then pick up a used set of stockers for cheap, send [i]those[/i] to the shop and not be without your ride for long.
Also: has nobody actually mentioned tire pressure, and, for that matter, tire design? there are tradeoffs here, too. Lacking a pyrometer, just try running your tires a bit over spec'ed pressure. There used to be a rule about pressure increase from cold to hot, but that was for bias tires and likely doesn't apply any more. If you've got a pyrometer, you want a nice even temp increase across the treads. And you want [i]dry[/i] air. Nitrogen is best. Scuba-air is second best (it's been very dried out). Otherwise, ask whoever owns the compressor if it's been drained recently. Try a body shop or garage where they're using pneumatic tools ,as moisture's bad for the tools. (time was, body shops were best because of the care they had to take for the paint guns, but they're not run off the same compressors any more).
Look at fuel mileage ratings the next time you're replacing a suit of tires - and remember that you're trading off mileage for something else, but for folks seriously considering some of the driving tactics advocated here, this shouldn't matter much.
Ditto aerodynamics. Air dams are easy to install, do actually work, even sub 65MPH. Get a flexible one so when you hit a curb with it when parking it won't matter.
Oh - and you could just buy a higher mileage car. My wife got one of the first US Priuses. She drives it hard and has been getting 50+ MPG for years now.
The rule I have always heard from car nuts is that you get your best mileage in the highest gear at the lowest RPMs. For my little 4 cylinder automatic, this happens around 40-45 mph, but I imagine for 6 cylinder cars it would be more like 55 mph or so.
Of course, this presumes that you are traveling at constant velocity. The folks who agonize over every mile per gallon will probably tell you that under normal driving conditions you can squeeze more mileage by adjusting the way you accelerate and decelerate (and how often you do so). Every time you touch the brakes, you're converting fuel into heat on your brake pads.
Traditional engines use less power ( thus less fuel ) to keep a car going over a certain speed.
Cars are geared for higher efficiency at certain speeds.
Problem is its all car dependent, with factors such as the age of the car tossed in. ( and what was the limits when the car was produced )
---- Booth was a patriot ----
Make those fuel consumption displays mandatory.
I've got an old (late 85) Porsche 944 project car. It has a fuel economy gauge below the speedo. I had no idea that this would happen, but it actually makes me drive differently. I suspect that it would do that same for many others as well. I find myself easing off when driving to try to keep it over 30 MPG.
Most BMWs since the late 80s or so have had these as well (likely because they were using a similar Bosch engine management system). This stuff isn't hard - you're absolutely correct. I suspect that most american cars don't have them because it would just be depressing. I know I don't want to see a needle on 10MPG all day long when I'm driving my pickup.
Do not fold, spindle or mutilate.
For me there is a mental cost to driving real slow and getting to your destination slowly. Lives are short. Get there as quick as you can. Time is more valuable than money.
If all combustion fuels cars were made with a moisture adding system the mileage improves significantly. A mist of water sprayed into the cylinder makes the combustion engines run much cooler (higher efficiency, shhh) but it also increases engine horsepower. The water is instantly flash-heated by the fuel explosion into steam for an instant expansion of 1:800 => making all your combustion engines be a partial Steam Engine by piping some H2O mist in through a vacuum tube port.
Interesting thing about putting real-time steam into a running engine is that the inside of the cylinder ~spark plug electrodes and everything~ is being STEAM CLEANED as the car runs. As to why Detroit has never done that I don't know. Perhaps our Big Three car companies hold lots of stock in ExxonMobil and Chevron... There's a lot of stuff not being done by Detroit. The government needs the tax monies for road repairs too much to do better so the amounts of fuel has been kept artificially elevated.
There's a WHOLE WORLD OF STUFF THEY COULD DO => http://www.askinventor.com/pdflistfor2008.htm . The system just can't take the lowered fuel tax monies right now {and reduced spa-massage-hooker-party hardy funds}. As for the rpm thing Mr. Smythe noted, my Suzuki 750 in 6th gear was only turning 550 rpms at 65 mph. It weighed 500 pounds, 770 with me on it. So if he leaves his sports car in 5th gear on the interstate at 2200 rpms he would likely get his optimum mpg AND be at a legal speed... instead of going into 6th gear at 85 mph. I used to run my bike regularly in 5th gear. The problem with driving in the highest gear is the engine is lugging at 55-65 mph, which means the fuel isn't being fully burned, which means carbon buildup in the cylinders and on the piston head. This is nothing but premature aging of the engine. However, if the moisture-adding mist system was put on his engine all that carbon buildup would be washed away by steam... or you could skip all the pain and build a car engine that uses fuelthatneverburnsup, and does have moisture.
Industrial Age 2 + How-to Stop Malignant Cancers.
Great fuel economy at 110MPH!!!
It's all about smart, non-aggressive driving, really. I remember a Car & Driver special a while back where they road tested a Chrysler with an aggressive driver against a non-aggressive driver and saved 20% on fuel economy. Unless you have a hybrid, driving at speeds under the limit (especially 55) isn't efficient, since you car's engine is the most efficient at 55 mph, hence the national speed limit set during the first oil "crisis." Drive smart, coast whenever you can, accelerate down hills to minimize resistance, and don't be aggressive.
Hehe ain't that the truth, though unfortunately going through the light just as it turns green can be unsafe if one of those all-too-common idiots who go through red lights is present.
That's exactly what the makers of the Kiwi were thinking - you get a 'Kiwi Score' to determine how eco-friendly you are:
http://www.thinkgeek.com/gadgets/car/ae12/
Here's THE book on efficient flying of a piston engine, but there is some applicability to driving:
"The Logic of Flight, The Thinking Man's Way to Fly"
http://www.propellersexplained.com/
It's recently written by Jack Norris, who (among many other things) was the technical director of the Voyager round-the-world flight. He knows more about efficiently running a piston engine through the air than anybody ever.
Here's a brief summary:
http://www.aopa.org/aircraft/articles/2008/080825asi.html
The key in long-haul driving is balancing engine efficiency against drag. Since drag goes up as the square of velocity, doubling your speed causes a quadrupling of drag. That's why driving more slowly, as long as you're in the top gear and running the engine efficiently, saves fuel.
Ecce potestas casei!
I love all the ideas about shutting the motor off while coasting. And discussions about turning off injectors. (You mean altering the timing? Or did they add like an off switch in the last few years?)
Best idea, don't stomp on the gas when you leave the line. Start saving to buy a Japanese built hybrid.
Whoever is doing that better not be in front of me unless they like the high-beams in the rear view mirror.
If you are driving that slow - you are too lame to drive - sorry, license revoked asshole
Its people like that that cause unrest
Can anyone tell that I live in Chicago?
---- "Logoff! That cookie shit makes me nervous!" - A. Soprano
I tried hypermiling in my 93 nissan altima last week on a few trips into town from the burbs, about 60mi/rt. Our city in the southeast was out of gas for the entire week after the hurricanes in Texas and I dreaded having to drive after hearing stories of the hoarders at the pumps(people filling up with 3/4 tank already, then filling their portables). I actually drove at the posted speed limit on the highway, occasionally powered off the engine and coasted to lights where I could see the other light's status, and turned off the engine wherever possible. Generally, I tried to keep the car at or below 2000rpm, which worked fine for driving 55mph. The result? 19ish-mpg, the worst I've gotten in the car.
That's still not as bad as people who brake when coming up to GREEN lights.
Oh, for mod points. Most people (well, most men anyway) are competitive, and we like to beat our "high scores".
LOL. You're absolutely right – and for some reason I think it's hilarious that the same reflex that causes men to accelerate when they're being passed could also help them improve their gas mileage.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
I've seen it both ways... like most people, I drive the same path pretty much every day. Three times a week I drive my son to an after school class that's about 10 miles away, and I drive the same way every time (barring unforeseen circumstances).
I know that if you accelerate rapidly from one particular light, for example, and get up to about 5mph over the limit, you'll make the next four lights, easily making it worthwhile for the extra gas used to get up to that speed. If you miss the light, you get stuck at least twice. That's just one example.
I also know the reverse is true... no matter how fast you go (within reason), there are times you will NEVER make particular lights and you'll definitely get stuck at them... but you never know if the guy behind you is going to make a right on red or something.
I also know that the morning and afternoon timing on the lights is different, and that the weekday and weekend timings are different. It never ceases to amaze me how people don't pay attention and figure it out... I know most of the drivers, like me, have driven that same way hundreds if not thousands of times.
So yes, more often than not I'm the guy trying to make the light... because even if I see red, I know it's going to change before I get there, and if you're going slow, you're going to make me miss the turn light. Thanks for being speed cop! If the limit is 45, I don't think it's wrong of me to reasonably expect you go to go somewhere around 45. And while I don't expect 0 to 60 in five second, 0 to 45 in ten or twelve seconds is not an unreasonable expectation when there are people behind you and you have no idea where they are going or where they might be turning.
Stupid sexy Flanders.
Actually, there's nothing that pisses me off than somebody who can't seem to anticipate the rush-hour traffic movement. They'll crawl until they have 2 or 3 car lengths, then they slam the accelerator, then the brakes, and then they poke around again until they've got room to gas it again. Driving behind somebody like that is hard as fuck if you're trying to avoid alternately gassing and braking yourself. Also, if you do try to maintain a more consistent speed, every time they peal out there's a huge space that other drivers will want to get into (which means you'll have to stop anyway because you were counting on using that space to coast while the moron in front of you is stopped...).
In short, you don't draft those people. You try to maintain a fairly consistent speed, since that's the best you can do under the circumstances – and as soon as practical you'd of course like to get behind someone else.
And don't engine brake because that is poor form and is retarded. Use your damn brakes.
Engine braking saves wear on your damn brakes and causes the engine to cut fuel flow (on a fuel-injected car). On a carbed car, it just saves brake wear while keeping your fuel consumption at idle level. I use my AC in conjunction with engine braking, so some of my car's forward motion is ultimately converted into cool air in the cabin.
http://www.ecodrive.org/The-golden-rules-of-ecodriving.249.0.html
(See bottom of page)
Also if you rev-match when downshifting, your engine braking will be smooth and well controlled, unless you straight shift without rev-matching which is poor form and is retarded.
"When information is power, privacy is freedom" - Jah-Wren Ryel
A long, slow acceleration up to a target speed will use more fuel than a rapid acceleration up to a target speed.
Sure, if you accelerate to 55 over a 1-mile stretch you'll use more gas than if you accelerate in a quarter mile. But then you also have to drive another 3/4 mile at 55 MPH before you can compare the gas use.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Most of the hypermiling I've read about is about increasing mileage, not about using less fuel. Some of the techniques involve driving out of your way if you know you can get above average mileage for doing so. To me, this is silly.
... eXtreme Driving? ...Lean Driving?
If you want to save money on fuel, use less fuel.
For example, because a warm engine is way more efficient than a cold engine, trip combining can be a big fuel saver. Similarly, with only a little planning, preparing dinner at home saves fuel.
Perhaps we should call this Agile Driving?
Maybe for YOU, you weak 75-pound pussy. Grow some balls!
There's also the throwout bearing that touches the pressure plate and the input shaft bearing that sits inside the transmission (gearbox) around the input shaft and spins on the front cover.
One time driving home for the holidays, I got stuck on a 350 mile drive in basically bumper-to-bumper traffic for 300 miles. I averaged maybe 25 MPH. This trip usually required 1.25 tanks of fuel in my 4 speed manual Tercel (at about 65MPH). When I got back - I still had well over 1/4 tank which was amazing considering there were long periods of stop-n-go. I was coasting with my foot off the gas quite a bit which would explain some of it. Driving 30 MPH on the highway is not practical - but it was an interesting case study in hypermiling.
From my own experience:
Tip 1. Get your engine up to optimal temperature for best efficiency. My commute is only about a mile and I get crappy mileage on these trips because my car doesn't have time to warm-up properly before I get to work.
So if you are running errands, combine them so your engine temp gets up to spec and stays that way for the duration of your trip.
Tip 2. Accelerate quickly, but smoothy. Don't jackrabbit/drag-race, but don't drive like granny. Imagine the acceleration curve as a nice, smooth curve towards peak.
Don't overaccelerate. Get to know how to get up to speed without having to brake to accommodate traffic ahead who don't drive efficiently.
Tip 3. Maintain a safe distance between yourself and other cars so that you can maintain a consistent speed.
Tip 4. Drive in the gear that provides the lowest possible RPMs for your speed. If you have an automatic, you can achieve this by lifting your foot slightly off the gas after you've reached speed and applying light, steady pressure to maintain speed. If you have a manual, you already know what to do... watch your tach and adjust gear/gas accordingly.
Tip 5. Inflate your tires properly (it doesn't matter what your political leanings, it's still good advice).
Tip 6. 55-65 MPH offers the optimal mileage. Go faster, even in a really aerodynamic car, and drag increases causing mileage to suffer.
I have an '86 Toyota Camry and a '99 Dodge Caravan that get 27mpg and 18mpg at 75mph. At 55mph they both get about 10 miles more per gallon.
Anything below that (like 45mph) and the mileage gets worse rather than better.
Just asking out of curiosity -- why do you say "partner" instead of "wife" or "girlfriend"? Is it simply to keep gender out of the discussion? I've noticed this trend recently, and I'm interested in why it's been on the rise.
Is that the British variant of what we USAians call a throw-out bearing?
Try a read of your car manual. Obviously, plenty of the "tips" in this thread contradict each other, perhaps some due to being incorrect, some dependent on vehicle, some for different typical journeys, whatever.
My car manual had sensible tips like:
- the optimal tyre pressure (winter and summer)
- at what speed it becomes more efficient to roll up the windows and use aircon;
- how often to clean the air filter;
- how often to replace spark plugs;
- how often to change oil, and what kind.
But best of all they were tried & tested for my car and did not promote unsafe driving.
Some more general tips included:
- remove roof rack when not in use;
- use a high gear, without labouring the engine, when on straights;
- drive smoothly;
- avoid turning the engine on until you intend to move off.
So MPG is not exactly great although I did get a couple extra MPG by adding a K&N Induction kit and replacing the mechanical fan (bolter to engine, always running) with an electric one that spends most it's time off when driving.
Over all I now get 17 MPG highway which is impressive considering the size of the roof rack.
In the not too distant future, next Sunday A.D.
...driving slower saves gas.
But drive slow enough to downshift one gear and all bets are off. Many ATs shift into overdrive at around 40-50 MPH, so staying above this shift point would be optimal (you can get an AT to upshift and then slow down somewhat and it will stay in the higher gear).
But I have a car (Porsche) that drops disturbingly near idle RPM in high gear at 60 MPH. About 70 to 80 is optimal for that car. Dropping from 5th to 4th gear (to cruise at a 60 MPH speed limit, for example) results in dropping from 18 MPG to 12 MPG.
Have gnu, will travel.
Four, if you need to stop suddenly, I hope you have strong legs. Those brakes don't work very well when your system isn't pressurized anymore.
Actually the vacuum reservoir on the power braking system has more than enough vacuum in it for one powerful stop (I guess that's what you meant by "pressurized"). If you press and release the pedal 2-3 times however, you'll be out of luck.
You're also wrong about the overheating - if your engine's about to overheat, coolant probably isn't flowing (or it's not flowing through the radiator due to a broken bypass valve) so turning the engine off is the best thing you can do, otherwise you'll just be allowing it to stew in its own heat rather than shutting down the action that's causing the heat. Your engine could get a little toastier than optimal running temperature if you switch off the engine and everything's working normally, but this isn't much of an issue.
Not that it's a good idea to switch off your engine while moving, since as has been mentioned before, you may need the power steering, you might need to power through a slide if the car goes sideways on ice, and you could accidentally engage the steering wheel lock.
"When information is power, privacy is freedom" - Jah-Wren Ryel
How does he expect his brake fluid to circulate?
Uh, brake fluid doesn't "circulate." It's basically a set of hoses full of oil, the brake pedal squeezes the oil via a hydraulic cylinder on one end and that pressure operates the brakes via another cylinder on the other end. Tiny amounts of fluid may enter or exit the hoses from a reservoir on the pedal end under certain conditions (assuming you don't have a leak), but it sure as hell doesn't "circulate."
I should share your post with some automotive enthusiasts, it would be an instant classic.
"When information is power, privacy is freedom" - Jah-Wren Ryel
The throwout bearing is also known as the Jesus bearing to those who wrench on cars. Usually after rebuilding the engine, installing it in the car, and topping up the fluids, you'll notice the Jesus bearing sitting on top of the toolbox.
So, it's named after what you say when you realize you forgot to put it back in?
I thought it was named because you pray that it doesn't fail. But I'm no gearhead.
The enemies of Democracy are
Men? Women do this just as often. I had one this morning go from 60 to 80 when I tried to pass and she did over 5 minutes at both speeds, so it wasn't an "accident".
Unfortunately the genius in the SUV is completely oblivious to the lesson. I love seeing people swerve in and out of traffic trying to cut that extra 2 seconds off of their trip, only to be the car in front of you stopped at the same stoplight. They think they're hot stuff but they saved no time at all, and likely killed their fuel mileage with the quick accelerations to dart around all of the cars to get there.
Idiots...
You'd probably have a fair to reasonable working knowledge of cars and car driving if you had a machine that used carbon ceramic discs!
Really not a good one. Try talking to people who own performance cars in that price bracket...more than half don't have a clue what's going on under the paint and would promptly plant their supercar in a wall if any one of the nannying devices were turned off.
Reminds me of a vid I saw of an old dude in a Ferrari F50 doing an autocross...he locked up the front wheels in a corner, and since the car was not turning or stopping his solution was to give it more brakes and steering. He hit a track worker (I think that's like 3 cones worth of penalties).
"When information is power, privacy is freedom" - Jah-Wren Ryel
Funny, but stop to think about it. You really don't think there's much tech-geek to car-geek crossover? What real engineer hasn't tinkered on an engine? It's in the fricken' title!
I think we need a new poll.
Highest level of car tinkering:
* The carwash changes my air freshener for me
* I've changed my own oil
* I've changed spark plugs and sensors
* I've performed a brake job
* I've rebuilt an engine
* I've rebuilt a transmission
* I've got a garage full of custom stroked and bored hotrod lead sleds.
* What with gas prices, I have to ride a CowboyNeal to work, you insensitive clod!
Personally, I've rebuilt an engine in a 1971 Volkswagen van, which falls about at the level of brake job for most other cars. I jest, it took about a week. I wouldn't touch a transmission, though, even if I had the tools.
I know a tech nerd who does have a garage full of custom and rebuilt cars, though. And I mean a big garage, he probably has about fifteen cars by now. Including a 1922 Pierce-Arrow he completely rebuilt.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
I have the charger daytona R/T, and before that had a regular charger R/T, both with Hemi's and MDS. I have gotten amazing mileage with both of these vehicles, 20 in the city and around 25 on the highway. I looked at all the other 4 door sedans and most of them even with v6's are way underpowered and get similar or worse mileage. I could be wrong, but I've never needed to use all the power the hemi has, so I generally barely put my foot down and still pull away from everyone around me...without even trying. The engines barely working though... which would explain the mileage.
We had a 1983 Cadillac Eldorado with the digital trip computer with instant and average MPG readout. After a bunch of measurements, and some derivatives, I discovered it got the best MPG at 45 MPH.
I've had lots of disagreements with people over the years. But so far, I have been the only person with recorded data to prove my position rather than seat of the pants opinion. Fun stuff.
80mph driving a 1.9TDI = 42MPG
I actually started doing this fairly recently in my Prius. One chunk of my commute upped its speed limit from 55mph to 65mph last winter and I noticed a drop in my gas mileage. A few months back, I decided to just move my ass over to the slow lane and set the cruise control for 55mph the whole way.
Result? I'm back to getting 51 miles per gallon in my Prius. When I was driving 65mph in the 65mph zone, I was getting around 46 miles per gallon.
(Also: the difference in commute time was less than three minutes total.)
I hit about 6 lights on the way to and from work each day and about two out of the 6 are timed right to cruise right through. I keep wondering why they don't have them timed better to avoid starts and stops and increase gas mileage. Sure, someone's going to suffer, but let it be the cross road traffic and not the main thru ways.
I'm a geek. I can do the math in my head.
I know what you mean.
I based my information from my logs. My log was kept at every refueling stop when I was making cross country drives. Basically, every stop was a fuel stop. More like, I only stopped for fuel at which point I'd eat, use the restroom, and maybe sleep. It included start and stop times, mileage, and the fuel pumped. I also kept the receipts so I could cross reference them in case of discrepancy.
Separately, I started researching the RPM vs fuel economy idea. At first my numbers seemed to be out of line with what people in general said (go slow, save gas), until I had a good set of numbers for various vehicles that reflected exactly what has been said along this thread. The gearing determines that cruise speed, which should be around 2000 RPM (+- 300rpm).
I just went looking around for the RPM compared to MPH, but couldn't find anything on that car. I did find the ratios, which we can use to calculate the RPMs, assuming you had all standard equipment in good condition.
2nd gear: 1.57:1
3rd gear: 1.00:1
4th gear: 0.67:1
Rear end gear (gas): 3.15:1
Rear end gear (diesel): 2.93:1
Tires: P225/70R15
In 3rd gear, you would be turning 1800RPM at 45mph. You were probably going too slow for it to shift up to overdrive. That, or something was stuck and it wouldn't ever shift up. Cadillacs in that era were famous for vacuum leaks, and just about everything is controlled by vacuum one way or another. If you could have convinced it to shift up to 4th, it's cruising speed may have been somewhere between 68mph (1800rpm) to 80mph (2100rpm). Because of the weight and wind resistance of that rolling box, I wouldn't think it would be in the higher part of that range.
And ya, my family owned several Cadillacs of that era when I was a kid, so I had a lot of experience fixing them. I learned a lot about chasing down cracked and leaking vacuum hoses on them. :)
Serious? Seriousness is well above my pay grade.
with an automatic. If I drive in the 70-75 mph range, I get 30-32 mpg. In the 65-70mph range, I get 34-36 mpg.
Well, once I was low on fuel but wanted to get home without stopping at a gas station, so I slipped into the wind shadow of a large truck (going at around 60 mph) and my MPH went up drastically. I don't remember how much but it was a lot.
Not sure I would recommend it for general purposes, though, since you almost have to be tail-gating the truck and can't really see what is in front of it. And he might get annoyed, but the guy in front of me didn't seem to mind. Make sure nobody is behind *you*, though, as you might have to hit your breaks hard if something goes wrong.
-Matt
Yep. The worst part is that you put the Jesus bearing on top of the toolbox, in plain sight, so you wouldn't forget to install it ... again.
Off topic, but coasting past a light that just turned green is more dangerous than most people expect. People who run red lights tend to do so right after their light turns red, and yours turns green.
If you're at a full stop at the light, the time it takes for you to accelerate into the intersection is typically enough to avoid the other car that's running the light, or at least respond to it. However, if you're coasting past the light, and especialyl if you're accelerating from the second the light turns green, not only do you lose that half-second delay to catch the car running the light, but you also have your foot on the gas pedal and are already moving.
Yes, the other guy might be at fault for running the light. But that's little more than a pyrrhic victory if you really think about it. The goal of driving is to get to point B from point A. If you end up in an accident, you might never reach point B.
"If a nation expects to be ignorant and free in a state of civilization, it expects what never was and never will be."
The most you're going to save is between 3-5 MPG, even less if you're in a big gas guzzler.
My assumption here is that most "hypermilers" are single-occupancy commuters. So here are my suggestions:
1) Carpool. 4 people in your pool saves you 75% in mileage.
and/or
2) Buy a cheap, small, fuel-efficent car (like Honda Civic), you can get 'em used for $500 and you WANT one that's fucked up. All that really matters is the engine. Then start losing weight. Strip out the interior including the back seats. Look at losing the bumpers and some of the panels if you can get away with it.
That's basically it. You can get 50 mpg out of a 1985 Honda Civic with little effort.
This tactic can be quite entertaining if, for example, an impatient bozo in a SUV comes up behind you while you're coasting, honks, pulls around you and speeds ahead only to stop at the light, and then you smoke him as you coast through the light just as it turns green.
Of course, that presumes nobody is in your lane or theirs, and they don't switch. Then you have to stop.
...then whatever entertainment value is thankfully and rightfully lost.
(-1, Overrated)
One more reason to stick it to environmentalists and choose Detroit.
Ride a bike...
How would I find out if a '91 Mazda 323 dose this?
The Mazda is manual; do automatic cars also do this?
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30mpg in a 5.7l V8 Firebird!? Highway driving at 30mph is not normal. I would have pulled over for a nap or to read. The truck driver could call about any problems.
My window sticker stated 19/28mpg. Those numbers are optimal and assumed unrealistic in the real world.
Edmunds specs the cars at 16/23 (very close to my numbers.)
Formula: http://www.edmunds.com/used/2002/pontiac/firebird/100002308/specs.html
TransAm: http://www.edmunds.com/used/2002/pontiac/firebird/100002310/specs.html
Consumer Guide observed ~16mpg:
http://consumerguideauto.howstuffworks.com/1993-to-2002-pontiac-firebird-4.htm
--
The Formula was a good deal. The extra $3000 for the TransAm added 50lbs for the rear spoiler and different nametags. No Formulas were available locally when I was searching. I have never seen a '99-'02 Formula; I check every time I see a Firebird without a spoiler. AutoTrader lists an '02 Formula just over 100 miles from here, and two '99 Formulas over 230 miles away (compare with 47 Firebirds and TransAms within 50 miles; 80 within 100 miles.)
My car is stock. Still has the skip-shift. I learned to skip second and third gears, only using them when I need to accelerate really fast. Tapping the gas pedal in first gear is enough for 20mph, then fourth can reach any legal speed in reasonable time. I learned second gear red-lines at ~50mph and third gear at ~80mph (both experiences were emergency manuevering to avoid accidents.) I cannot imagine maxing fourth gear -- probably hit the 167mph limiter first.
What causes the difference in our fuel efficiency? The hills around my home? Your customizations? Attitude?
I spend my life entertaining my brain.
4500 pound cars?
My TransAm weighs 3300 pounds. Most other people I've compared notes with (and checked the door tags) are 2900 to 3500 pounds. The Toyota Prius weighs in at a hefty 2700 pounds. To get into that range, you're looking at a SUV.
Serious? Seriousness is well above my pay grade.
Hi All:
The Readers Digest article involved me and no, I am not the only diver on the road but one who follows the speed limits in the far right lane while RR and will pull a reverse pass or alternate if needed. What are the results? I drove from Chicago to Cincinnati and back to Chicago in the std. 05 Accord ov erthhe past two days and it allowed 51.5 mpg. Following the speed limits is not only legal, it is safer than driving 5, 10, 15 or more over the limit.
85 mph will not give you better FE than 75 better than 65 etc.
Engine Braking w/ Fuel cut is a momentum killer and although not as bad as the binders, it is not a good technique for max FE.
P&G'ing to 75 and back to 10 mph would not optimize FE.
Good Luck
Wayne Gerdes - Owner/Admin www.CleanMPG.com
Slow driving you burn more fuel in relation with high velocity, the reasons are the RPM, in higher RPM the motor uses more fuel, so, you can drive slower in 2nd gear and 4000 RPM and will burn fuel than 4th gear and 2000 RPM.
1010011010
I'm amazed that the optimal speed range is 40 to 60 mph (or 65 to 95 km/h).
In the town where I live here in Brazil the speed limit is 60 km/h (or 37 mph). Now I know that I'm consuming more gasoline than I needed.
If it's not bad enough, lots of places in the city have some obstacles in the streets to force the drivers to slow down even more. Some of them have some sense, specially near schools, but some are just stupid.
Look what I'm talking about:
http://www.colider.mt.gov.br/home/images/img_releases/0DSC06914.JPG
http://www.capitaldopantanal.com.br/imagens/ntc_27973_quebra-molas.jpg
I have a Dodge Magnum with a HEMI and if I drive 65-70 on 101 from Salinas to San Jose and then 680 to 80 and then Sacramento I get 25 MPG but when I take I5 the MDS won't work since more throttle is needed for all the hills. The MDS comes on when 15% or lower of the throttle is used. On I5 I get 19-20 MPG going 75-80 as the speed limit is 70. I make an effort to drive more efficiently on the freeway and if I am sane on the city streets it does 17 mpg. The smaller 3.5 liter has 100 less horse power and almost 175 ft lbs of torque less but only 1-2 mpg better. But I did not buy a HEMI to get great mileage. I got it because I really like driving this car.
The economy benefit comes from engine braking being s-l-o-w, so you learn to get off the throttle sooner. It doesn't matter if you turn kinetic energy into hot brake rotors via friction or hot air via compression, either way it's disposed of (OK, maybe 30% gone if you have a hybrid or EV with regenerative brakes). Using engine braking discourages you from charging up to the red light under power, then braking hard only when you must. Downshifts don't save fuel, you can get the same savings by braking early and very gently to stop in the same distance as you would with engine braking. They just teach you to plan ahead and make better use of the energy you expended accelerating up to speed.
Engine braking is the way to go for descents in the mountains, even with an automatic transmission (it has PRND L for a reason). Besides keeping the friction brakes cooler, not riding the pedal constantly makes the brake lights meaningful to the driver behind you. If the brake lights are always on, they are just as useless as if they don't work at all.
for my car, Mitsubishi Spyder, they recommend shifting into 6th at about 50mph. So basically my interstate driving is all in the top gear by far. At 70-75mph driving on WV interstate highways I get about 20-21 MPG. If I just drop my speed to 65mph everywhere I go during a tank of gas I can reach 24 MPG.
I get 12 to 15 km/litre in a Holden Astra (1.8 petrol) at 120 km/hr (75 mph) here in Queensland Australia.
I can get into 5th gear (top gear) as low as 60 kmph (40 mph) on the flat for cruising at 2500 rpm. I downshift to accelerate.
In-town fuel efficiency is rubbish because Brisbane has traffic lights everywhere; generally down to 9 km/litre even though my best average speed is 55 kmph and often as low as 40kmph. I thus burn more fuel for longer.
I submit that inefficient and outdated traffic control systems contribute 10-50% of traffic emissions of a developed nation, depending on the quality of planning and the degree of urbanisation.
I like to give a little "yoo-hoo!" drumming-fingers-in-air wave and a happy smile as I coast past them onto the roundabout at 35.
Everything I needed to know about life, I learnt from Blake's Seven
You incredible morons driving slow to save money make me laugh. Do the fucking math. You are going to save 5 cents driving slow, but lose 10 minutes on your trip? Fucking retard. Get away from me, I don't want to be associated with anyone that fucking stupid.
The way the motor labors is attached to fuel efficiency. A vehicle with an engine in it that has the required amount of power for the weight of the load/vehicle will be more efficient than one with an engine that's not powerful enough. Likewise, type of vehicle matters. Those in SUV's, pick-up trucks, etc. will get less mileage than those in compact cars. SUV's and pick-ups are built to haul loads and will have engines that can pull more weight and will use more gas. As for fuel efficiency and motor labor, I've found that in an automatic, you have certain spots where your rpm is higher because the motor has to work harder. Go a little faster and you can get to where it kicks into another gear, which will reduce the rpm's- thereby reducing the usage of gas. In a manual transmission, there's a perfect spot to shift at. You have to watch the rpm guage to find the right spot, as well as hear/feel the operation of the engine. Shift too soon and the rpm's are too low and you have to use more gas to keep it running/speed up. Shift too late and you're using more gas before you shift because the motor is running harder. I think the one car I had with the best gas mileage was my Honda Civic Wagon. The thing was Forest Service green, with road stripe yellow pin stripes on it but it ran great and got great fuel economy. This was a manual transmission and because of that, it had the 1500 motor and not the 1300 motor my brother's 1983 Civic had (his wasn't a wagon style, as well as being automatic transmission instead of manual). I always averaged 45 miles to the gallon on mine and my brother averaged 40 on his. Personally, I think the 1300 motor wasn't quite enough power and the 1500 was perfect for the Civics. Now, because it was an early 80's car, it still had a carburetor- NO fuel injection! The same goes for my brother's Civic he had. Those cars were great for most driving and fuel efficiency... I really miss mine. They also almost never broke down. My brother ran his engine to 450 thousand miles before he had to rebuild it. I had to change the catalytic converter on mine (which was bolted in and really easy to change) but other than that just had to perform regular maintenance. There's another way to cut on gas usage. MAINTAIN YOUR VEHICLE! Maintaining your vehicle will always raise your mpg and lengthen your vehicle's life. What else? Don't drive crazy. Only haul things if you need to. (If you have a ton of stuff in the back but don't need to transport it anywhere, clean it out.) Here's something most people do wrong... oil changes. Oil change recommendation is three-thousand miles or three months- WHICHEVER COMES FIRST! I always did monthly oil changes and every other month, I replaced the filter. Many people let that go for much longer than it should. One guy I worked with had let his oil go for so long that it wasn't liquid anymore. It was solid, in clumps and sticking to everything inside his engine. He had to have the whole engine taken apart, cleaned out, re-bored, etc. It was a lot of work that didn't need to be done if he had just changed his oil. Oil pans and filters... Many people won't clean out their oil pans and change the gaskets. How do you think it leaks oil like a sieve? Where do you think that dirt came from? Oil filters should also be changed. The time it should stay in the vehicle depends on the filter you buy. Some are better and some are worse. However, if you do your own oil changes, filters are dirt cheap and it's not hard to change it every oil change or every other oil change. Air filters. This is possibly the easiest thing to tell if it needs a change or not. Do you see bugs in it? Can you actually see light come through it? Does it look horribly dirty on the paper? You tell me... Not changing this can adversely affect your fuel consumption. CHECK IT REGULARLY! Every time you do an oil change is a great time to do so. Fuel filter. If this is clogged, your car won't run right, may stop (act like you don't have gas) and can waste gas by forcing the
Hey, i've read some comments here, and here is my piece of knowledge.
Speed and consumption are not related in a fixed equation. What defines the consumption of an engine (of any engine) is the torque that it gives in the output AND the revolutions.
So this means, that yes, your consumption is related from your speed (revolutions of the engine), but also relates with the gear your gearbox is engaged in (both in Auto and manual cars), and to the torque that the engine is giving at the specific time.
To make things more simple: If you are driving with 60 mph, you can be consuming nearly 0 GPM (if you are going down a hill), because the torque of your engine is close to zero. On the other hand, if your going up a hill, then your consumption is increasing cause the torque that the engine needs to give in order to lift the weight of the car up the hill is great.
Other things that influence the consumption is the condition of the tires, the aerodynamics of the car (that's why when you're close behind another car you consume less), the weight of the car and other factors that increase the demand of torque from the engine.
One of the things that increase the demand of torque is also the acceleration: the bigger the acceleration needed the biggest the torque. But the consumption doesn't follow the same rule!Each engine has a chart, that shows what is it's consumption at any revolution with any torque at the output. And that's the reason why it's so difficult to define how to drive with low consumption.
Hope i helped :)
Keep your speed constant; fluctuations up and down are bad.
Even in the city? Sometimes I slow down when approaching a red light so that I arrive behind the stop line or the vehicle in front of me right as it turns green, without having to come to a complete stop. But a lot of times when I do this, people illegally and dangerously cross the double yellow line to try to pass me. Should I be trying to prevent this?
There are already laws on the books that handle slow drivers. In most areas that I've driven in, the minimum speed is 10 mph under the speed limit (in the United States).
What provisions do these states make for slow-moving vehicles, especially bicycles and horse-drawn vehicles?
Indeed, every time you touch your brakes you waste gas, provided you're not driving a hybrid.
Free Martian Whores!
hehehehe :-)
We don't believe in radical loony monotheistic religions from the middle east -- we're Christians.
I have a degree in engineering, but it's been a while.
Simply saying 'traction and friction' isn't a rebuttal. The AC's point is a bit counterintuitive, but in general, dynamic friction is pressure * patch size. But the pressure is weight DIVIDED BY patch size. So the patch size typically makes no difference to friction in conventional braking - it's weight of the car (plus any spoiler force) * the frictional coefficient of the tire to the road surface.
CHEAP tires make a huge difference, because their interaction with the road surface is inferior. Performance cars, as I understand it, have much GRIPPIER tires (the rubber is different) and those tires are much wider - partially because the WEAR IS directly related to patch size, and the larger tire lets them be grippier without disintegrating immediately. Tires are pretty complex technology, overall.
In my opinion, patch size CAN make a huge difference in nonconventional braking - that is, braking edge cases. On snow, I've seen massively better performance from a SMALL patch size (relative to vehicle weight) because the car will tend to sink farther into more solid material (until you bottom out!) I believe a large patch size similarly increases your chances of hydroplaning. On the other hand, a large patch size makes it much less likely that smaller transient factors will affect you - e.g. that if there's just a very small patch of ice or slick spot or loose road surface on part of the patch, the impact is lessened. And I'd say it definitely increases your chances of getting more EVEN acceleration/braking, by averaging out small scale road conditions.
I get the feeling large patch size might have additional advantages for advanced all weather technology (the ability of the tire to act like it's not in water by channeling water away, etc.)
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