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2 In 3 Misunderstand Gas Mileage; Here's Why
thecarchik sends in this piece, which was published last March but remains timely: "OK, so here's a little test: Which saves more gasoline, going from 10 to 20 mpg, or going from 33 to 50 mpg? If you're like most Americans, you picked the second one. But, in fact, that's exactly backwards. Over any given mileage, replacing a 10-mpg vehicle with one that gets 20 mpg saves five times the gasoline that replacing a 33-mpg vehicle with one that gets 50 does. Last summer, Duke University's Fuqua School of Business released a study that shows how much damage comes from using MPG instead of consumption to measure how green a car is. Management professors Richard Larick and Jack Soll's experiments proved that consumers thought fuel consumption was cut at an even rate as mileage increased."
News at 11!
I don't know if changing the units will help much ..
I get that the 1st one is a 100% increase while the other is only 50% but you still get a better deal and less pollution by buying the 50 mpg car (if the price is the same).
So which saves more gasoline? the 2nd one ...
Breaking: In an astounding fit of partial international cooperation and scientific rationality, the US adopts a mostly metric measure of resource use: the milliliter per mile, or the mlpm
For example:
10MPG = 378 mlpm
20MPG = 189 mlpm
33MPG = 115 mlpm
50MPG = 76 mlpm
90MPG = 42 mlpm
The unit is linear, easy to understand, with numbers everyone can grasp (40-400 ish), and most important, it slowly creeps the US mind toward the metric system, one small step at a time! What a breakthrough! When the cars fly, we can try for using km, not miles.
Also, mlpm helps put the idea that gasoline is a great resource, to be used sparingly, by the milliliter, as opposed to "by the gallon" like 7eleven slurpies.
Sadly, in all seriousness, from TFA "Consumption instead of mileage? Nah. Dumb idea. Never work. [sigh]" Probably have to agree with this. Not because it's a dumb idea, but because Americans with the social and business systems in place have shown repeatedly that they will hold onto current ideas so strongly even in the face of overwhelming and obvious evidence showing them to be wrong. Only the real American idol will effect real change in the US system, the dollar.
There are always proposals to replace MPG with gallons per hundred miles or something of that sort, since the latter would show the even decline. That said, it's mostly immaterial; the measurement doesn't match naive expectations, but it's still accurate. Increasing MPG means using less gas, and people aren't likely to think about it in terms more detailed than that.
$_ = "wftedskaebjgdpjgidbsmnjgcdwatb"; tr/a-z/oh, turtleneck Phrase Jar!/; print
I always thought that measuring it Euro-way - in, for example, gallons per 100 miles - would me more practical and clear.
Though it may not be obvious why to someone in a metropolitan area or Europe.
MPG is the more useful number when you need to figure out what the range of a vehicle is (and perhaps if you'll be able to reach the next station). In the western US it's not unheard of to find yourself 100 miles from any gas station.
"Prefiero morir de pie que vivir siempre arrodillado!"
News at 11.
An alarming number of folks suck at everyday math, and the worst part is that most don't even realize it. Instead we see them taken in by false sales, and easy to see through misinformation all the time.
I'm not sure if I should call them fools, or try to sell them something?
Which saves more gasoline, going from 10 to 20 mpg, or going from 33 to 50 mpg?
people answer incorrectly because the question is academic. what matters is that people know a higher MPG is better, which i think almost everyone does.
My zoned high school (which I thankfully did not attend) boasted a 30-40% "at or above grade level" scoring rate on the statewide basic algebra exam, at least as recently as 2005. This was considered an improvement over the rate from the 90s, which hovered around 25%. I am not at all surprised that so few people can see through a basic ratios problem like the one given in TFA, even though my high school is (hopefully) not representative of the norm.
Palm trees and 8
If you go from 10 to 20 mpg, youre still less than the 33 mpg lower limit in the second case, so the second option "saves more gas". If the question is "which is a bigger improvement in fuel economy", then the answer is the first one.
Probably have to agree with this. Not because it's a dumb idea, but because Americans with the social and business systems in place have shown repeatedly that they will hold onto current ideas so strongly...
Believe it or not, we have a way to fix that. Change the EPA's guidline to "your cars must get at least X miles-per-gallon" or "your cars must get no more than X gallons-per-mile" Watch how quickly the new number gets onto your local dealers' showroom floors.
In fact, the two cases are not interchangeable. Suppose the problem is dressed up a little: you have two cars that you use on a regular basis (this is not negotiable), but only enough money to replace one of them. One car gets 33MPG, and the other gets 10MPG. If you replace the 33MPG car, you can get a 50MPG vehicle. If you replace the 10MPG, you can get a 20MPG vehicle. Which would save more gas, replacing the 33MPG car or the 10MPG car?
Palm trees and 8
Or Americans, since any (Real) American should be able to tell you that a 12-gauge shotgun is bigger than a 20-gauge shotgun. Point being, we use units which are inverse of intuitive, and don't seem to have a problem with them.
I say this as an American who thinks the gauge system is weird, the mileage system only slightly less weird, and guns rather silly...
I think the point was more about what should be prioritized when it comes to replacing vehicles; you cannot get everyone to replace all of their cars at the same time. So, if you are working on a policy for the US government, what sort of policy should you push? You could give a tax credit to everyone whose vehicle gets more than 40MPG, but what about all of those people who need a large, less fuel efficient vehicle? They won't have any incentive to replace their guzzler, even though it would be a lot better for them to do so.
Palm trees and 8
That people are this stupid in such great numbers. FFS I could have done the math (and I assume all my classmates as well) back in 2nd or 3rd grade. How do these idiots manage to survive?
WTF's a milliliter?
by Mike Buddha -- Someday the mountain might get him, but the law never will.
The article says "here's the math" and then proceeds to offer an example involving not math but arithmetic.
Whether the fuel consumption ratio is expressed in distance per volume or its inverse is not as important as the simple recognition that it's a ratio. But when people blithely speak in terms such as "five times less" there is bound to be a fundamental confusion between ratios and differences.
Parity: What to do when the weekend comes.
Change mpg to gpm.
But most people do consider cars in the same class with similar mpg ranges. So more likely you would be considering a 21mpg vs. 19mpg or 30mpg vs. 28mpg. Since there's a big difference between 21 and 19 and not so much between 30 and 28 (even though the difference APPEARS to be 2), I think having customers understand this IS huge.
If this pushes the states to change units it would convince many thousands of people to look into being more fuel efficient and could result in many millions of dollars saved.
But then America is still trolling the rest of the planet by using imperial so I doubt they'll be switching anytime soon.
They're also kinda bad at pluralization.
Parity: What to do when the weekend comes.
why not use what the rest of the world uses: liters/100km
How does the difference between a factor of two vs. a factor of 1.5 translate into "5 times"? Some kind of crazy "MBA math"? ;-)
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
...maybe a computer science analogy is what's needed to fully understand the concept?
This is why I prefer the Litres per 100 KM. It solves the problem this article describes.
Plus 'Gallon' is ambiguous.
ie) In Canada car ads often use imperial galons, but you may also see an American ad that uses US gallons. You have no way of knowing which the ad intended.
There is only one definition of Litre.
end of message
$/year is best unit, everyone understands that.
unfortunately that's not constant across users.
no, the issue is that gallons per 100 miles is a useless number. Well, no, I retract that -- it's a useless number for everything except comparing fuel efficiency between two cars, which, uh, you can do with MPG pretty well. honestly. there's really no use for consumption/distance. nobody has a 10mpg car and a 33mpg car and needs to know if they'll save more going from 10->20mpg or 33->50mpg. That's just a ridiculously contrived scenario from someone who I presume is primarily motivated by their self-induced woes over how unlike Europe it is here in the states. Gigantic eye-roll here.
Seriously. Outside of a math problem for school when would ANYONE ever need to figure any of that out? It's useless information for consumers. So long as there's SOME sort of scale showing its fuel efficiency, you can tell which cars will go further for less. Current car gets mileage X; new car A gets Y, new car B gets Z. That's only 3 vehicles. If X is 10 and Y is 20 and Z is 50, Z will be the greatest increase. Because X always is the same!
And if, somehow, someone IS trying to replace one of two vehicles and needs to know which to replace to save the most money, going by the straight-up percentage increase in efficiency over some distance is NOT going to give you the right answer anyway. USE needs to be taken into account; that is, if you've got a 10mpg car, and a 33mpg car, and the replacement for each respectively would be 20mpg and 50mpg, knowing the percentage increase for replacing either is useless unless both vehicles are driven equal distances. If one is just for hauling heavy loads and the other is the daily use car.. 100% vs 50% increase doesn't matter, you'll get more savings (most likely) by going with the 50% increase as that vehicle will be used much more often (not to mention that 20mpg is going to go down if in fact it is going to be used for hauling or pulling heavy loads -- because most likely that 10mpg your current large vehicle gets is NOT what was on the window when you bought it but rather the actual realized mileage you have been getting with it).
Rant off. This is just another Euro-superiouritist. I just made that shit up. Fact is this guy is creating a contrived scenario that has no bearing on anything in the real world, and while it makes me weep a bit for the critical thinking skills of my countrymen it's just not an issue that ever has any bearing on anything outside of the math skills of the Man on the Spot. I think we all already are aware that if you pose a math problem to random people, most are going to get it wrong. That's not even a uniquely American phenomenon. This guy just needs punched in the teeth I think is what I'm trying to get at here.
... still waiting for this free-as-in-beer free beer I keep hearing about.
...but is there really an issue with being drawn to the higher number (50, as opposed to 20) as long as the terms remain the same and the outcome is reduced consumption?
Is lack of account for fuel consumed while idle, stopped, coasting, or stopping.
Saying "20 MPG" is oversimplistic.
Who ever travels 20 miles without ever having to stop or change speed?
Presumably efficiency is not the same under all these conditions.
If you travel to a fast food restaurant at lunch time, and go nowhere fast in line for the drive-up for 20 minutes, and when you get back, your odometer shows you drove 10 miles.
Is not going to have the same fuel consumption as simply driving 10 miles down the highway.
In this case, the measure of MPG is extremely inaccurate for the vehicle that has an inefficient consumption while idling.
Whereas, it could be pretty close for the vehicle that automatically shuts down or conserves fuel while idling.
In fact, the vehicle that's more efficient at idling could have an average lower consumption in the real world, even if the MPG are slightly poorer than another vehicle, that is inefficient for the load being applied to it.
The European way:
Gazoline need for 100 miles:
@10 mpg: 10 gallons
@20 mpg: 5 gallons... saved: 5 gallons, 50%
@33 mpg: 3 gallons .... saved: 1 gallon, 33%
@50 mpg: 2 gallons
kinda more intuitive.
The Cloud - because you don't care if your apps and data are up in the air.
A mile is an imperial unit used nearly ubiquitously in the USA.
The British no longer use it because their empire collapsed. Since the US is the last major imperial power, we still use the imperial unit.
"I don't care about the Constitution!" --Bill O'Reilly, November 17, 2009
...a vehicle that gets 10mpg is likely driven more miles than a vehicle that gets 50mpg (I'm thinking Bus/tractor trailer vs. mini-cooper/Prius). Given that, then going from 10 to 20 is more fuel economical than going from 50 to 100.
OK, so we got too problems.
You either don't have kids or your kids must not have friends. The seat belt laws limit the number of passengers per vehicle, so when you need to pick up their 6 friends, you're 3 seats short in your Prius. Are you going to drive that 2nd car to transport them? The minivan is probably better than an SUV for that since it gets slightly better mileage.
Just 25 years ago, you could cram them all in a 4 door Sedan since they could squeeze in or sit on each other's laps. I remember riding in a station wagon with 12 other kids. It was cramped but not against the law back then. If anyone sees that these days, they'd call the police and have that parent arrested for child endangerment, all in the name of safety. Now the most you could fit is 8 passengers in a minivan. A full sized gas guzzling van could hold more passengers.
They're only just bringing back some station wagons with 3rd row seats for 3 extra passengers. Otherwise, you'd have to get a minivan to transport the kids and their friends.
So what if people can't do fractions right in their head on the fly clearly they forgot to figure in inflationary gas prices.
given 10,000 miles at $1.5 per gallon 1980's
18 mpg = 555 gallons = $832.50
28 mpg = 357 gallons = $535.50
Savings = $297
give 10,000 miles at $5 per gallon Worst Price in the last 5 years
34mpg = 294 gallons = $1,470
50mpg = 200 gallons = $1,000
Savings = $470
give 10,000 miles at $3 per gallon Todays Price
34mpg = 294 = $882
50mpg = 200 = $600
Savings = $282
So do you want to save $292 in 1980 or do you want to save $282 at todays $3 per gallon or do you believe prices will go up to around $5 and thus save $470. So depending on how you want to twist the number you're saving the same amount roughly or your saving a lot more for option B vs option A
I have two children. One is a boy born on a tuesday. What are the odds that the other is a boy?
Precisely the same question, and for precisely the same reason....showing off mathematical quirks, it has nothing to do with MPG calculations other than showing they involve maths.
Please consider this account deleted, I just can't be bothered with the spam anymore.
Probably because most folks in the US have no idea how far 100km is. Liters they only know of because of pop/soda.
They're also kinda bad at pluralization.
Not to mention statistical reasoning. "most Americans would fail 6th grade math..." yet somehow, most Americans have passed the 6th grade.
"I don't care about the Constitution!" --Bill O'Reilly, November 17, 2009
Clearly, what we need here is a car analogy!
Anyone?
Cheers,
"What in the name of Fats Waller is that?"
"A four-foot prune."
How much fuel is saved by replacing a vehicle that gets 10 MPG with one that gets 50 MPG?
The answer should be getting rid of the 10 mpg car and getting the 33 mpg or 50 mpg one. Why create the illusion that getting the 20 mpg car is a good choice? You know at least one person will actually think it's a better choice to go out and buy the 20 mpg car.
So... you want to change the units used so that people don't make wrong basic assumptions? Perhaps investing in a better education system so people don't end up thick as **** and misunderstand elementary maths might be a better long term plan? Then you won't have to worry about changing every other metric used in daily life... Anyone tried asking a cross section of the public in the US whats better for their waistlines - changing from eating 70g to 45g or from 250g to 200g packets of potato chips...? Are KCal's simple enough or should you change to a kind of unit that takes into account portion size too?
Sure a somewhat facetious example but hey, where do you draw the line under ignorance?
regardless of the units. The real takeaways from this article are that mpg is a stupid unit to use, and that most people don't understand per units at all.
Of course, when cars fly, km won't be relevant because the international standard for aviation is nautical miles and velocity in knots.
--Jim (me)
My car gets 40 rods to the hogshead and that's the way I likes it.
It's the wrong question.
The question should be which one uses more gasoline...
two cars. one uses 20 mpg. the other uses 50 mpg. which one spends the most on gasoline for, say 100 miles.
Privacy is terrorism.
You do realize that the current EPA fuel economy sticker already has a consumption measure -- in terms most people understand more readily than gallons-per-mile -- dead center, right?
It called "Estimated fuel cost per year", and the units are dollars.
honestly. there's really no use for consumption/distance.
Well, there's one very obvious usage for this...
USE needs to be taken into account;
Yup, that's it. consumption/distance is useful when taking into account usage. You see, people seldom wander aimlessly with their cars. Most of the time, they follow quite usual pattern. (Hence, all the "people's locations are highly predictable" that pop-up regularily on /.)
So you want to compare usage of cars ?
You know where you live, where you work, other places where you go regularly. Thus you know what average distance you travel by car on a regular basis.
So you know how much you travel per week, or how long it takes to total 100miles 8or km).
When the distance is known, using cons/dist it's pretty much trivial to compute how much gas you would need for your given weekly usage. And then computing the costs of said gas is easy too.
Of course, as pointed by others, the dist/cons form is useful when computing the range of a vehicle.
"Sufficiently advanced satire is indistinguishable from reality." - [Tips: 1DrYakQDKCQ6y52z6QbnkxHXAocMZJE61o ]
No one cares about proportional improvements, they'll look at the headline figure - whatever that happens to be for all the cars they are interested in and rank them accordingly. In this case as 10 (v. bad) 20 (pretty awful) 33 (now we're getting somewhere) 50 (OK, that will do). It sounds to me as if this professor doesn't understand how people make decisions and is, himself, too bogged down in the trivia of the numbers (or is trying to be too clever by half - it doesn't impress, BTW).
politicians are like babies' nappies: they should both be changed regularly and for the same reasons
50 mpg car is better?
For some values of better... like fuel efficiency. I am sure it is worse for some things.
This issue is a bit more complicated than you think.
You know what else shows the "even decline" -- and uses units that are more familiar to people and more directly state the personal impact? Stating the estimated fuel cost in dollars/year using consistent assumptions across a class of vehicles.
Which, incidentally, the current EPA fuel economy label already does. So the complaint that we need a prominent consumption measure instead of a mileage rating is misguided -- not because we don't need to have a consumption measure on the fuel economy label, but because that's what is already dead center on the label.
sell the 10 MPG car and buy the 50 MPG car!
So long as there's SOME sort of scale showing its fuel efficiency, you can tell which cars will go further for less.
I think the point here is that the MPG scale is not linear, while a GPM scale would be. This would make comparisons far easier to understand in terms of typical costs.
Man who leaps off cliff jumps to conclusion.
I did get the question correct, instinctively. But, the factor of 5 was much higher than I thought would be quipped as a difference.
What the article says is true: Going from a 10 miles per gallon car to a 20 mpg car saves you 4.85 times as much fuel for any trip as does changing from 33 mpg to 50 mpg. However, it might be worthy to note that the first change lets you use 0.5 times the fuel for a trip, while the second change lets you use 0.66 times the fuel. And so, you could say that the first switch lets you use 0.16 times less fuel than the second switch. That's the factor I was thinking of.
Well, I suppose the point of this article is a way of conveying long term fuel use in a way easy to process and compare in somewhat complex ways in the average American's head.
The article's idea for gallons per 100 miles (gp100m?), where smaller numbers are better, seems nice. If we used that, then you would be comparing switching from 10 gp100m to 5 gp100m, and from 3.03 gp100m to 2 gp100m. With this metric, one can easily and quickly see that the first switch gives a bigger difference in fuel use, the difference being that the first switch saves 3.97 gp100m more than the second switch.
Using gp100m does avoid the problem that this article pointed out, but is there any other problem of perception and comparison that might arise? Also, does the quick and dirty comparison using gp100m above give a good representation of intensities in the comparisons?
You've got the units wrong. It needs to be measured in dollars per mile. To 90% of people, it's the deciding factor in the end.
Ideally, gas pumps would electronically transmit how much you spent filling your tank, and your car would have a little display that shows the money draining away. When the gauge says broke, your car is too. Maybe link the GPS into it, and it can show that you have enough in the gas tank to get to Joe's house, and putting in the tank the $3.82 in change from your last $10 you will have if you buy the 12 pack instead of the $5.54 in change if you get the 6 pack will give you enough gas to get you home but is not enough to get you to work in the morning too. Personal circumstances may vary, but damn, I know a few people who could use that system.
This sentence no verb.
Actually the British still hang on to miles for distance measurements.
(and feet and inches and pounds, but that's a separate kettle of fish)
Man who leaps off cliff jumps to conclusion.
This is an attempt by professors at a "prestigious" university to attempt to make the rest of United States citizens look like a group of brain-dead monkeys. The fact of the matter is that the second one does save more gas. How much you improve a car means shit; the important number(if there really is one in this discussion, as "green" is total horseshit) is the end result, not by what percentage you increase gas mileage. I know that this group is talking about actual gas saved, not the difference between the two in percentages, but the whole idea is messed up.
No matter what uptight idiots that are highly educated want people to do, people will continue to consume. In order to help save people money, it simply makes sense to go to the highest mpg-rated vehicle possible. I am against the whole "green movement", as it endangers people's way of life and causes too many people to lose jobs. That is, not to mention to detrimental effect on people's wallets in the name of a bullshit idea and junk science.
If people were looking to be saver(which a majority of ALL citizens, not just United States citizens, fail at doing), then they would follow the amount of fuel they are using and limit it only to what they can afford to budget. Since this is not the case, then it is dumb to rely on sticking people with 20 mpg cars when the market is able to reliably offer 50 mpg cars. Yeah, people will travel more, but at least they will be able to afford it more. To me, it sounds like the oil industry just gave Duke a large infusion of money.
Just as an aside, miles per gallon(MPG) IS the measure of consumption of a vehicle(though it is lacking some measurements). What else are these lace-curtain homos wanting? Do they want to measure how many Greenpeace assholes a car pisses off? Perhaps they want to measure how many "My Little Ponies" a vehicle eats in order to travel over a given distance? Perhaps(in all seriousness) car manufacturers could measure consumption by [volume]/minute, but that will leave off information too. What if you drive for four minutes, eight seconds? Going 30 MPH will consume less per minute than going 50 MPH, or 70 MPH. Sure, the calculations will vary, but US citizens are too dumb to take that into account(sarcasm, for the dumb), right?
The fact is that mpg is the best calculations(to date, of course) that a vehicle manufacturer can provide. The manufacturers could give estimates on how much it will cost, on average, to sit at the average length of a traffic control light(i.e., "red lights"), but that will not really help. What about traffic jams or other times that you sit in a car while it idles(traffic stops for citizens and/or law enforcement)? The fact is that they do not provide answers, they(the school) want to see itself in the news.
How about this school use that brainpower to find answers to more important problems. That would include almost everything else that exist, including how Lindsey Lohan might be able scam her SCRAM braclet and how to plug the whole in Heidi Montag and Spencer Pratts marriage(and maybe one of Heidi's breast implants).
That people throw out a perfectly good car that gets 25mpg for a new car that gets 30mpg and think they're saving the environment. They never consider the amount of fossil fuels that went into mining the materials for their new car, what went into building it, testing it, and then likely shipping it across the ocean. Buy a good car, learn how to use a wrench and keep it running and well tuned for 30 years and you'll be doing the environment more of a favor than buying a prius. Although, you wont have your "Im green" badge to drive around.
it certainly does not fly
http://www.popularmechanics.com/home/improvement/energy-efficient/4350335
every day http://en.wikipedia.org/wiki/Special:Random
The US created a system called EnergyStar back in the 1990s and it's used internationally so you likely have heard of it. For a long time PC BIOS would show an EnergyStar logo, even in countries where EnergyStar was otherwise absent. I'm surprised you have not heard of it in Australia, because it is a registered trademark in your country and it was likely slapped on various appliances and electronics you imported from Asia through most of the 90s.
“Common sense is not so common.” — Voltaire
Only the real American idol will effect real change in the US system, the dollar.
Aw, I thought you were going to type Kelly Clarkson.
Anything can be found funny, from a certain point of view.
Don't get me wrong, if you're looking at replacing a perfectly good car with a new car, knowing how much better that car is is compare to your old car is a very useful thing.
That said, if you need a new car anyway, it really doesn't matter that the difference between a 10 mpg car and a 20 mpg car is higher than the difference between a 50 mpg car and a 33 mpg car. I 50 mpg car is still the best choice. No you probably shouldn't throw out your 6 month old 33 mpg car to get a 50 mpg car, and no you shouldn't say "I can't afford the 50 mpg car so I'm going to stick with the 10 even though I can afford the 20", but while mpg doesn't scale linearly, 50 is still better than 33.
there's a thousand of them in your coke.
Don't forget stones!
The usual measure for aircraft is quantity of fuel per hour, not per distance. And the fuel may be measured by weight, not volume, since that's more important in determining range and runway lengths.
And why does the ratio even matter? We're trying to measure the absolute benefit of increasing fuel efficiency here, not the percentage. The point is that going from 9 MPG to 10 MPG gives you greater monetary savings than from 100 MPG to 1000 MPG, so we should concentrate on getting rid of the low-efficiency cars rather than skimming off milliliters from cars that are already ultra-efficient.
Try an example of 100 miles: 100 miles at 10mpg = 10g. 100 miles at 20mpg = 5g. So, savings of 5g. 100 miles at 33mp ~= 3.3g. 100 miles at 50mp = 2g. So savings of ~1.3g. But 5g / 1.3g != five times the savings. Roughly 3.5 to 4 times the savings (without breaking out the ol calculator).
Yeah, but I think it should be *grams* per mile (or km, league, chain or whatever). The energy per mass is invariant over habitable temperatures, so it'll be harder to get ripped off by buying a car in the winter time and then measuring it in the summer.
Can you be Even More Awesome?!
The ultimate way to get 2 idiots who agree with each other to argue.
You do need a pretty large, high riding vehicle if you have difficulty bending down or standing up while moving laterally; a motion commonly required to enter and exit these smaller, low slung vehicles.
seriously... Fuq U A business school? how unfortunate!
Woah, woah. You expect us to be smarter than a sixth grader?? That bar's a little high, don't you think?
Can you be Even More Awesome?!
and will be using it to track my latest.
The first car I tracked was a 2007 Civic Coupe EX, manual transmission. The second was a 2008 Mazda Miata SE. Without bouncing to the site to check the Miata was rated at 21c and 28h. In my two years of recorded mileage I never fell below 27 in a mix of city and highway travel; I have a 26 mile commute mixed between 35 and 55 with no interstate. I peaked at 33 during summer months and fell into the 27 range during winter where besides the cold requiring the engine to run rich I needed the compressor to run the defroster.
My newest addition, a 2010 VW Golf TDI with manual transmission shows that others have never been as low as the EPA predicted mileage which is 30c and 41/42h. I have yet to finish my first tank and the car's computer shows 38 miles per gallon.
Why all the fuss? Well the facility is there and it gives me a nice reference to see how my car reacts to seasons and how it reacts to age to include over all miles traveled. It provides a nice little log so I can also see fluctuations in fuel prices without having to rely just on my memory; like what was the price of gas in June 2008.
While many cars are not represented it does appear those with cars known to get good mileage do post their numbers more often. I have been surprised while browsing some vehicles to see just how low the mileage ratings are for many popular sedans, in many cases not better than many SUV/CUV types that people love to vilify.
* Winners compare their achievements to their goals, losers compare theirs to that of others.
The Duke school of business could have been more subtle about how they feel about other business schools. Did they have to put Fuckya right in the name? Couldn't they have put that message in a motto or by-law or something?
nobody has a 10mpg car and a 33mpg car and needs to know if they'll save more going from 10->20mpg or 33->50mpg
I have a compact and a minivan. I drive the compact to work, my wife lugs a small army of children around in the minivan. While the numbers aren't quite 10 and 33 (the minivan is better than 10, the compact isn't up to 33), the stated scenario isn't absurd. And I don't believe I'm particularly rare.
William of Ockham had no beard. The most likely explanation is that it was chewed off by squirrels every morning.
anyone else love the way in the uk we use mpg, but petrol is sold in litres, so a gallon is utterly meaningless to most britions...
Well, if the US would just adopt something slightly less silly like "gallons per thousand miles", it would be a huge improvement. That or maxbe the speed limits should just be expressed as "minimum 60 seconds per mile".
Opus: the Swiss army knife of audio codec
It's not that people don't understand MPG
It's simply that people don't understand percentages or ratios. This is a question of math.
"All great wisdom is contained in .signature files"
The depth of a joke that EnergyStar is was put in stark relief when the GAO (through a fake company set up for this very purpose) managed to get an EnergyStar label for a gasoline-powered alarm clock.
The
Which one saves more gas:
a) replace a 10 mpg car with a 20 mpg car.
b) replace a 33 mpg car with a 50 mpg car.
From the way the question is posed it is impossible to say. How many miles-per-year does each drive?
The Americans are still - in 2010 - discussing cars that do 10 or 20mpg. 40 years after putting over a dozen people on the moon, and getting them home in one piece.
Here in the UK, you'll struggle to see a car on an everyday basis that achieves figures that low. Sure, abusing any car will give terrible mileage. But I'd take a guess that well over 90% of cars sold here(UK) in the last decade would hit 30mpg with town use, and 40mpg on a run - for a petrol. Stick 5-15mpg on both figures for a modern diesel.
I'm not talking about small cars either, with those figures. 5-seat family cars with decent storage space.
Tell you what, if those guys will switch to metric the rest of the world will forgive the wrong spellings, all of them.
If God forks the Universe every time you roll a die, he'd better have a damned good memory.
When the cars fly, we can try for using km, not miles.
Your car is a hog.
ID: the nose did not occur naturally, how would we wear glasses otherwise? (apologies to Voltaire)
For that reason, the vehicle registration pricing structure in most countries is usually nonsensical. You have to pay additional vehicle registration for each vehicle you own, registration which will cancel out any economic benefit from owning other vehicles with better gas mileage. e.g. if you own a small car, it could conceivably save a lot of money, fuel and CO2 pollution to also own a 100cc motorbike (e.g. Honda Supercub) for local trips in good weather. Depending on where you live this could be up to 90% of the total distance travelled, and only using 1/6 the fuel. This works out to be no additional burden on the infrastructure (usually less), and better for everyone. However, unless the registration policy changes, it is a very economically marginal thing to do.
The same concept applies to owning a big vehicle for work purposes or infrequent use. There is little incentive to buy a smaller car to run around in, because the registration cost is large. It would make more sense to pay one registration per person if you own a vehicle, and that includes any vehicles you own. Or even a subsidy for owning certain classes of vehicles, e.g. 100cc motorbikes. If a registration subsidy for owning a Supercub was almost the depreciation + maintenance cost for owning one, a lot more people would own one, and use one. Every km travelled in such a vehicle is saving 90% of the fuel that would otherwise be used. That one administrative change could potentially shave a double digit percentage reduction off petroleum usage.
This would also mean LESS waste in the production of new cars. A bike like the Supercub uses a fraction of the resources to create as a car. And if the car is only getting half the annual km on it, then it is going to last a lot longer.
If I have seen further it is by stealing the Intellectual Property of giants.
Another question with a non-obvious answer: you're going on a 100 mile trip. You drive the first 50 miles at 30mph. How fast do you have to drive for the rest of the trip to average 60mph the whole way?
Dear Slashdot: next time you want to mess with the site, add a rich-text editor for comments.
Wow! So I guess I should trade in my 35mpg car for a 20mpg car!
Really now, how is this helpful in the least? If I acquire a car that has a higher mpg rating than my current car I am saving MORE gas, so do I really care what happens from 10-20? No.
is whats being moved per gallon. I often have love children accost me because I drive a large diesel truck but it gets 18mpg with 6 people 4 dogs and bed full of camping gear. My buddy takes his subaru and his brothers toyota pickup to move the same amount. Who's doing better ?
Si vis pacem, para bellum! For evil to succeed good men need only do nothing!
From the article:
But like it or not, lots and lots and lots of Americans need large vehicles for their jobs, their families, and their lives.
There's some serious weasel word action going on in there ("lots and lots" is horribly unspecific and leaves the author lots of room to wiggle out of fact-checking, but it sure sounds important to the reader), but let's be honest: only a small percentage of us need big cars. Most people seem to buy cars based on maximum anticipated usage ("You know, I do landscaping once or twice a year, I should get the SUV," or "We get the neighbors together and go camping once a year, we need the room.") rather than what they use the vast majority of the time. While I certainly know people who need the large vehicle, most of the people I know how have them practically never need the size or power.
One thing we can do to help the fuel efficiency overall is not buy this way and plan on renting the larger vehicle now and then we need it. It's getting easier: I've noticed a lot of hardware stores rent pickups now.
The article actually generally pissed me off because it presents a false dichotomy. Yes, going from 10 mpg to 20 mpg saves more gas than going from 33 to 50 mpg. But how many people face that decision? Most of us are either buying a new car entirely (so not replacing one at all) or we're replacing a specific existing car, so the first mileage is fixed. You'll always do the most improvement by going to the highest mileage, in either case.
The only times this comparison matters is if you're asking which vehicle to replace (when you have a free choice) or if you're asking where the auto industry should focus on improvement. The latter is mostly out of our hands and the former practically never comes up, in my experience.
A while back I ended up having to make a graph of MPG and gallons of fuel consumed assuming a fixed number of miles driven to illustrate this to people who didn't get it.
Mileage.png
Coding with assembly is like playing with Legos. Coding an application in assembly is like building a car with Legos.
I see no problem with MPG. MPG are a better indicator of what's going on, since it doesn't lose sensitivity so quickly. One has to understand that as cars get more efficient, they are asymptotically approaching some limit. A linear scale doesn't work, unless you start piling up digits after the decimal.
Let's say that Prius does 4.5l/100km in some driving scenario. I highly doubt that a non-plugin hybrid, of a certain mass, driven in similar scenario, will ever do, say, 1l/100km. I'm too lazy to get real numbers out of my ass, but some things just don't change -- even you you drop rolling friction, assume ideal thermodynamic efficiency (with realistic materials, though, no 5000K cylinder walls, please), get some 50-years-in-the-future drag coefficient, you still won't beat some number. Ever.
Thus the closer you get, the smaller the difference will be in linear terms. MPG, OTOH, will keep going up while still needing no more than 3 digits: 999MPG is 0.24l/100km, and you will simply not get a car that good. A change from 100 to 101MPG is 0.02l/100km, and a change from 200 to 201MPG is 0.006l/100km. IMHO it's more manageable to use MPG since you need three digits for realistic scenarios and that's it. Heck, it's rather rare when you can definitely say "xxx is enough for everyone" and be right -- with MPG, it's just that. Perhaps with some very, very clever computer control (automatic pilot), you may need one more digit of accuracy (MPG with one decimal). You need really repeatable driving for that, and here humans just won't do.
So, by the time you need xxx.x MPG format, we must have pretty much cars that drive themselves, and are linked in (ad-hoc?) networks that optimize traffic flows for energy efficiency. Human drivers are abysmal when road utilization is high: traffic jams are caused by human drivers, not by anything that's somehow inherent in the road or high traffic flow. The control loops in our brains are poor enough to cause problems when the bumper-to-bumper distance gets small and the speed is "high" (think freeway). When traffic is flowing well, humans still are notoriously inefficient drivers, but the good flow gives an impression that things are just fine, when they are in fact far from optimal. Very far.
A successful API design takes a mixture of software design and pedagogy.
Its a non-linear scale so not everything is shown. http://www.answers.com/topic/nonlinearity
so a compromise has been made here between information needed and too much detail
but if you were to "generalise" (I know bad [hides] ) its still true that 33 miles per gallon is better than 10 miles per gallon.
I have to hope that the Slashdot summary is not how they worded it to individuals. I read the summary and thought "duh, in the first example the car gets double the gas mileage. In the second example, it was not quite double - 66 would be double. So the first one was a bigger improvement." But then I knew something had to be wrong with the obvious intuitive thinking, so I spent 5 minutes on paper making sure I canceled my units right.
And the obvious answer was it!
Looking at the article...
proved that consumers thought fuel consumption was cut at an even rate as mileage increased.
It is! Doubling the gas mileage saves half the gas! I'm don't see the logic hole! What am I missing?
And finally, we all begin to understand why cash-for-clunkers program focused so much more on how "bad" the old vehicle was, rather than how "good" the new vehicle is. When you look at replacing millions of cars, the greatest consumption decrease comes from getting the worst of the worst off the road forever, even if they are not replaced with 50MPG cars.
The TFA claims that
There are now a few moves toward putting consumption on window stickers, right next to mileage.
The silly thing is that fuel consumption is already on the labels and has been for years. Look for "estimated annual fuel cost".
Absolutely. I can't believe everything it's pointing it out.
And the point of the article is idiotic. He is unsuccessfully trying to argue that the inverse of mpg is a more informative number when it's the same number just inverted. Sounds like an oil company spokesman attempting to point out that a less efficient vehicle can be cheaper for you. By the same argument you could get a rebuilt car down in Mexico that costs $5000 and will last 20 years with $500 a years in maintenance but only get 5 miles to the gallon. Being wasteful can be cheaper, what a novel concept.
MPG displayed on the dealership sticker is an estimate and the one shown in the dash is an even worse estimate.
6.8SPC TR of 550, l xwind at 6, drift rt at 26" drops 77". AT has 503 ft-lbs at 1403 fps. FT 0.86
It's 62 miles. I just round to 60 when I'm doing stuff in my head. Not exactly terribly hard to envisage - it's very roughly "the distance you drive in an hour" in most places.
Americans I've met often like to think of miles as minutes (40 miles? That'll take 40 minutes to get to). So 100 km should be an easy measure for Americans to understand. It's essentially "hours", using the same reasoning.
The hypermilers extol the virtue of slowing down to get better mileage out of a car but none of the information is factored out over time.
It's a perfect time for being wasted.
A perfect time to watch the stars.
- Burden Brothers, "Beautiful Night"
ridiculous exercise in misleading semantics is this article? Seriously?
From their example..
A 20mpg car takes 5 gallons of gas to go 100 miles. A 50mpg car takes 2 gallons of gas to cover the same distance. I understand the mathematical misdirect they are trying to make, but it seems like a 'feel good' rationalization for low mpg vehicles - "hey, it's not so bad.. it's 50% better mileage than your old clunker". But who really asks a question like 'Which saves more gasoline, going from 10 to 20 mpg, or going from 33 to 50 mpg?' when you're focused on bottom line mpg. It's dealer-speak for the small-minded.
At the end of the day, a 50mpg car used 8 gallons of gas less than a 10mpg car to travel 100 miles. Everything else is usedcarsalesmanspeak.
Ad revenue ploy.. good times.
The designer wants the smallest tank he can sell in the market, because it occupies precious volume and has weight. It's not just the weight of the tank wall itself, but the weight of the entire volume of car structure that surrounds and protects the tank. If you simply expanded the volume the cheapest way, you would lose the cargo volume of the vehicle. Increasing the car body size to compensate will add a lot of metal and glass. Also, you have to engineer the tank and support structures to handle its weight when full, so that also increases the weight of the supports beyond merely scaling by surface area...
If we just switched it to gallons per mile instead of miles per gallon, we'd still have the same linear progression and not have to change all pumps and road signs.
My blog. Good stuff (when I remember to update it). Read it.
You could replace your 10 mpg with a 50 mpg car or do the unthinkable (especially in urban areas) and replace the car by a most fuel efficient bike, which runs on pizza (at least for /.ers). This also save you extra exercise in the gym. And most important, regular every day use of muscles is more important than 1/2 in a gym. And if your sweating by doing so, its either hot outside and your antiperspirant failed or your so unfit that you really should replace the car with a bike. ;-)
To figure out the average of two vehicles with MPG1 and MPG2, the answer is not (MPG1 + MPG2) / 2. It's 2/MPGavg = 1/MPG1 + 1/MPG2.
e.g. Say a family has vehicle 1 which gets 50 MPG and vehicle 2 which gets 10 MPG, and both are driven the same distance each day. Your average MPG for both vehicles is not (50+10)/2 = 30 MPG. It's 2/(1/50+1/10) = 16.7 MPG.
I think this is the bigger problem with using MPG instead of GPM. To the mathematically disinclined, MPG exaggerates the benefit of having a high mileage vehicle (people think they can offset using a gas-guzzling SUV by buying a hybrid for commuting), while downplaying the disadvantage of having a low mileage vehicle (people think trading in their old 14 MPG SUV for a 12 MPG SUV is not that big a difference in gas mileage).
Not sure if anyone's mentioned it already, but you can view the problem as a variant of Amdahl's law.
Outside the US & UK, fuel consumption for cars, trucks, etc, is normally expressed as Liters per 100 kilometers. This completely avoids the non-issue that TFA is grumbling about, even for innumerate consumers, since the numbers represent fuel used in a trip of 100km.
10 miles per US gallon = 23.52 L/100km (mind-bogglingly bad)
20 miles per US gallon = 11.76 L/100km (very bad)
33 miles per US gallon = 7.13 L/100km (OK for SUV, not so good for a car)
50 miles per US gallon = 4.7 L/100km (good for medium or large car, not so good for compact car)
FWIW, my Mercedes diesel stationwagon uses about 5.5 L/100km for mixed city/rural driving, which is 42.8 mpg(US) or 51.4 mpg(UK).
Those who can make you believe absurdities can make you commit atrocities. - Voltaire
How about 'gallons per centi-mile', with abbreviation gpcm. Then you can laugh at the people who get metrically confused and think it stands for 'gallons per centimetre' or 'gallons per cubic metre' [or 'gallons per cubic mile'] -- although the 'centi' prefix is more of an SI thing, and less of an imperial thing.
Ask me about repetitive DNA
Fuel savings are generally built into the perceived market value of the car. All else being equal, the more economical car will often cost its entire lifetime of fuel savings more than the less economical one. It's crucial that you track the future value of money when making an assessment. That extra $$ you spend (or finance) up front comes at a cost that can easily dwarf your lower operating costs.
> Which saves more gasoline, going from 10 to 20 mpg, or going from 33 to 50 mpg Now if I move from 10 to 20 mpg: To travel 100 miles, I will be using 5 gallons If I move to 50 mpg: To travel 100 miles, I will be using 2 gallons So definitely 50 mpg is better in terms of 20 mpg. Who cares what percentage of fuel I am saving? If I go by TFA, moving to 20 mpg from 10 mpg is better, since I save more % *compared* to my earlier mileage. However, I still end up burning more fuel compared to 50mpg
I had to cringe when you said "is underfunded and overstretched". Really this sort of organization shouldn't require any funding, and should simply use trademark rights to assert licensing terms with partners (manufactures, building contractors, etc). EnergyStar *almost* operates that way right now, given that it is a voluntary program.
UL(Underwriters Laboratories) is a private entity that required certain specific safety testing to be passed by a product before the UL logo can be placed on that product. They have a fairly narrow scope though, mainly for fire safety. But it is one of only a few testing labs recognized by various local building codes in the US as well as federal organizations such as OSHA. Testing fees are modest, and the organization is able to scale with demand.
Another example with is Snell. To use their logo on your helmet requires specific tests, the tests are fairly expensive so not all helmets are Snell certified, but part of their budget funds helmet safety research.
Why EnergyStar can't operated the same way, I do not understand. It seems like if we had an international standard (one of the positive aspects of EnergyStar) that provided oversight and certification of various testing facilities to authorize them to grant limited rights to licensed partners to claim certification would be scalable and efficient.
With an obscure government entity there are almost always problems with oversight and responsibility. When EnergyStar gets in trouble there is no CEO or politician to blame, it's all just faceless bureaucrats. In situations like these it is the media's responsibility to expose failures in a bureaucracy, but the side effect is consumer trust in the EnergyStar brand is damaged. A business operates differently when trust in a brand is important.
“Common sense is not so common.” — Voltaire
Can this be the reason why the industry uses mpg instead of consumption.
No can't be! The car/oil industry is so nice, they would never do that....
Cars like Opel/Vauxhall/Chevrolet Zafira has been available since -99 and has 7 seats and does 39MPG, no need for minivans.
- Raynet --> .
Why is the article - and this thread - making a big fuss about what is basically a trick questio.? The cries about innumeracy are predictable, but wrong. Given the nature of the question almost anybody is bound to understand it as "Which will be more fuel efficient: 20 MPG or 50 MPG?".
I am pretty sure that other trick questions can devised to foil similarly the consumption based rating.
cheers,
alf
...I think I understand the root cause of the idiocy of it.
It was written by "Management professors" - WTF ?
Is it just me or is that a stupid question?
A 50mpg car is more 'green' than a 20mpg car. Who cares what you replace what car with what. MPG is a helpful pointer to how much fuel you'll use. If you replace a 10mpg car with a 20mpg your fuel usage is still going to be far too high in my view.
Sterilise your children.
Better yet, see Seth Godin's piece from last August: http://sethgodin.typepad.com/seths_blog/2009/08/not-so-good-at-math.html (and the math - http://charliepark.tumblr.com/post/169016492/in-seth-godins-post-this-morning-he-talks-about & http://www.onpreinit.com/2009/08/mpg-illusion-seth-godin.html)
antipaucity
I'm in a country where liters/100km is the norm, and I think ml/km would be rather more elegant. Having a number within a unit seems rather odd. Sure, ml/km trades the number for an additional prefix, but unlike numbers, prefixes are not unusual in units; and ml is one of the most common units (in metric-land). Furthermore, the range of values is more practical: 6l/100km corresponds to 60ml/km.
Switch back to Slashdot's D1 system.
it slowly creeps the US mind toward the metric system, one small step at a time!
You mean, like, inch by inch?
Life is wet, then you dry.
A bit of a tangent but I have increased mileage per tank of fuel on my car by 16% simply by knocking 5mph off my 'motorway' speed (65mph) and changing gear at 2,500rpm instead of 3,000rpm. I average around 37-40mpg.
330 miles per tank up from 270. 1.4l 2002 Ford Fiesta (UK).
And this is why GM did hybrid SUVs first. Something that people thought was stupid. Replacing a Tahoe with a Hybrid Tahoe saves way more fuel over the life of the vehicle than replacing a 25-30mpg car with a prius - or even an imaginary car that requires no gas at all.
The geek button got pushed, wherein a false item was offered up as fact, and the overpowering instinct to raise one's hand in class and correct it illustrates a fundamental piece of social programming common in many.
Even when they know it's redundant, that it's not going to be read, (let alone noticed), and will generally only add to the clutter of a forum tree which is already populated with 750 comments and growing, they'll go ahead and do it anyway. Such is the auto-response system of the common nerd.
And people wonder why I insist that the human race runs almost entirely on automatic. This is just an extreme example. Virtually all behavior is automatic. (Including this one, btw. My auto-button activates when I see thoughtless behavior. I chose to indulge it this time and write this response.)
-FL
so what your saying is that 10/20 is a LARGER difference than 33/50??? that 1/2 is less than 2/3!?!? that if you only get half the mileage that is worse than getting 2/3 the mileage!?!?! really? Im going to need to tell my friends about this.
It’s a matter of what’s important.
In Europe, with relatively high gas prices, relatively dense cities, and relatively short commutes, the most significant part of your daily commute is the amount of gas you burn, i.e. how much it costs.
In the US, with relatively low gas prices and spread-out cities that weren’t designed to give low commutes, the most significant part of your daily commute is how long it takes to get where you’re going.
As a result, in the US you’re more concerned with “how long can I drive between fill-ups?” (miles per gallon) whereas in Europe it’s “how much will this trip cost me?” (litres per mile).
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
litres per mile
Er... what the hell was I thinking?
Let’s all just pretend I said litres per hundred kilometers...
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Yeah. My Walk-in refridgerator is EnergyStar on a per-volume-cooled basis, but running it still dims the local streetlights.
I can't figure out why.
Where are we going and why are we in a handbasket?
I've driven a Prius in both Australia and in the US. In Australia, the car reported in liters per 100km, as TFA reported, which kept be completely confused. I find the L/100km about as useful as a speed limit sign stating hours per 100 miles.
Right -- and higher octane allows for higher compression. The LS3 in my 2010 Camaro SS has insane high compression, partly compensted at low rpm by big cam timing, and knock sensors and all that -- Basic thermal stuff says efficiency goes way up with compression, very quickly, which is why Diesels do so well (but stink in other senses). But because people built cities in stupid places in CA where there's thermal inversion, the higher NOX output of high compression engines was basically mandated out of existance. Here in farm country, having nitrogenous fertilizer fall from the sky in the rain seems like a somewhat better idea than in LA, home of the **IAA and other "nice" outfits. And the Camaro (422 hp they say, and I believe that may be an understatement) gets over 3 mpg *better* mileage than my 2007 6 cyl Honda Ridgeline....Which doesn't hold all that much more cargo, but at least has back seats larger then infant size. These mileage numbers get even worse when long high speed trips are measured. The Camaro mileage goes way up on the highway, and the Honda gets even worse. 98% of my driving is on twisty mountain roads, though.
Why guess when you can know? Measure!
You either don't have kids or your kids must not have friends. The seat belt laws limit the number of passengers per vehicle, so when you need to pick up their 6 friends , you're 3 seats short in your Prius. Are you going to drive that 2nd car to transport them? The minivan is probably better than an SUV for that since it gets slightly better mileage.
And there's your problem... why exactly do you need to pick up 6 of your kids friends? Why can't THEIR parents drive them to whereever they're going? Why can't they take public transport or walk (if it's less than 5km or so)? Why can't they take a taxi (if you live in a place where public transport/walking is dangerous)? I'm assuming these kids are all friends because they know each other somehow... and they probably know each other through a shared activity (such as school, hobbies or sports), so it should be reasonable to expect they've got alternate arrangements for making it to those places... getting whereever to hang out with your kid(s) should be the same.
People in the rest of the world seem to manage to have kids with active social lives without needing a minivan/SUV...
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You see, it's all about smiles per gallon. That's one of the main reasons I stick with my old 60s junk. Big block truck gets 12.5 MPG, big block car gets 17 MPG, straight six compact car gets 33 MPG, 4 cyl bike gets 42 MPG. All are 60s vehicles, and some are my daily drivers. I refuse to buy anything fuel injected or emissions comtrolled to drive every day. They're fine for toys, but I need reliability simplicity and depndability for something I drive every day. I need to know that it will start and get me to where I need to go every time, and the occasional failure will be quick/cheap/easy to fix. I'll tolerate fuel injection and emissions controls on a toy, as I don't need to depend on it. It it doesn 't start, oh well I either figure it out or do something else that day. As for CAFE, that was the single worst thing for fuel economy. It killed good 25+ MPG full size stationw agons and replace them with 10-13 MPG SUVs. Thanks big government for your intrusive and detrimental regulations.
Actually the British still hang on to miles for distance measurements.
I guess that means they're hanging on to their imperial ambitions as well. Should the US beware of a UK resurgence? Probably.
"I don't care about the Constitution!" --Bill O'Reilly, November 17, 2009
The article's math is silly. You don't look at the percentage of increase for the best gain. You look at the total gain. Going from 10 to 20 miles per gallon increases your range by 10 miles per gallon, an increase of 100%. Going from 33 miles to 50 miles increases your range by 17 miles per gallon, but is only an increase of 52%. And you still want to argue that 10 extra miles per gallon is somehow better than gaining 17? Nonsense.
So I guess if I have an SUV that gets 2 MPG and I can get it to go 5 MPG, that beats all the options?
Idiot.
"They said I probly shouldn't fly with just one eye," "I am Bender. Please insert girder."
the example is a bit deceptive, its tempting to conclude the first is better because it is a greater percentage change, but going from 10 to 20 is still better than going from 33 to 99 in terms of gallons saved per mile. Traveling 100 miles in a 10mpg, would take 10 gal; 5 gal in a 20mpg; 3 in a 33 and 1 in a 99 mpg car. So you save more gallons per distance in first case even though second is a bigger percentage improvement. right?
My car gets 13500 cubits per sester of phlogiston-infused fuel!
Bow-ties are cool.
A liter is about 1/4 the size of a gallon, so all cars would have very low ratings if they said miles per liter, or KM per liter. A SUV that gets 12mpg would get about 4 KM per Liter and a honda that gets 30mpg would get about 10 KM per Liter. And with everyone saying why dont we just get the people who get 12mpg to get 50, your not gonna get bubba out of his super duty and into an insite or jetta tdi. If he is a contractor or got a nice bass boat, he will in fact need a truck that gets poor mileage.
I thought it was short for CC?
by Mike Buddha -- Someday the mountain might get him, but the law never will.
You do realize that the current EPA fuel economy sticker already has a consumption measure -- in terms most people understand more readily than gallons-per-mile -- dead center, right?
It called "Estimated fuel cost per year", and the units are dollars.
The problem with that figure is that it has to be based on some set cost per gallon of gas. That means that, periodically, those figures are going to change. Then years from now, when I consider buying a new car, it makes it more difficult for me to compare my current car to cars on the market because the 2 figures are based on 2 different cost-per-gallon figures.
So I buy a car with a fuel cost of $925 per year, then in a few years I'm looking at another vehicle with a cost of $1160 per year? The baseline gas price used to generate the estimate has gone from $2.82/gallon to $3.77/gallon. Now, quickly...without pulling out your calculator, tell me which vehicle is more efficient, and how much more efficient is it?
The summary neglects to mention the number of miles for each vehicle, making it impossible to compute the right answer, even for a mathematician. The amount of fuel used can be computed as miles divided by miles-per-gallon. A 10-mpg truck that is only used for 20 miles in a month consumes only 20/10, or 2, gallons during that month. A 33-mpg car that is driven 1500 miles in a month consumes 1500/33, or about 45, gallons each month. (BTW -- I have a 10-mpg truck, which I actually *NEED* once or twice a month to carry something big or heavy. The rest of the time, I drive a car.)
This entire discussion about how best to present the concept of "fuel efficiency" so that that the average innumerate American will best understand, really misses the point. The only numbers that most Americans seem to understand are the ones that have dollar signs in front of them.
The only question to which most innumerate Americans will listen to the answer is, "How much does it cost?"
So, the only way to present this information that those Americans will understand, is using units that involve dollars.
Most people will understand "dollars-per-mile", or "dollars-per-thousand-miles".
How is mlpm easier to understand when auto efficiency and roads in the USA are measured in gallons and miles?
Wanna know a secret? MPG and miles are also linear!
"mlpm helps put the idea that gasoline is a great resource ... unlike 7-Eleven slurpees"
WTF? You think that if you sliced the unit to 1000th of a greater unit it makes it more sacred? LOL. Have you ever looked at the psychology of currency? The smaller the unit, the less people care about it. People throw pennies in the trash! I would wager that the opposite is true. If I had only 1 of something, I would treasure it more than 1000 littler somethings. I could afford to lose a few hundred of the littler somethings because if I round up I still have 1 something.
A slurpee is ~1/4 a gallon ... using your logic, we should measure fuel in "slurpees" because its a smaller unit!
YOUR ENTIRE ARGUMENT IS SUBJECTIVE to the units you are comfortable with. A liter is about 34 ounces (~1/4 gal) - or about 1 Big Gulp Slurpee and an extra sip! LOL. Europeans are already using the slurpee-unit!
If you want to make something sacred, make it expensive and harder to obtain. Like the diamond industry does. Oh, that's right they are ripping us off when it isn't necessary!
*
Regardless, the real solution to the perception problem in the post is to upgrade from a 10mpg car to a 50mpg car. Arguing that the 10-20 path saves more will only encourage people to drive 20mpg cars rather than 50 mpg cars.
These upgrade paths measure % improvement, not actual savings. A 33mpg saves more than the 20mpg car - without upgrading at all!
The MPG scale *IS* liner. Sheesh - what do they teach you guys in Europe!? 1mi +1mi = 2mi. 1gal +1gal = 2 gal.
fuel/distance is useless for the driver. A driver says to himself when he is at the gas station, "My trip is x miles and my tank holds y gallons. How many gallons does it take to get to x?" ie mpg. x, the distance, is the constant - and desired goal. Not the available fuel.
No one gets in their car and says well, we can only go to Knotts Berry Farm because we don't have enough gas to get to Disneyland.
All you guys are doing is inverting the ratio and changing the units. Gallons versus liters is irrelevant because gal (u) = L is simply gal = (1/u)L
You have to understand the US ratio x distance per 1 fuel-unit. You guys are saying y fuel-units/100 distance. We literally say "more miles to the gallon" as a perfomance ratio. Its an encouraging statement.
Saying "less liters to the 100km" is psychologically depressing. Everyone wants "more", not "less."
How big would Billy Idol be if he sang, "In the midnight hour, I want less, less, less..."
No, it's still dumb.
You've now converted percentages to the number of gallons it would represent in savings;
This is what was presented in the article. If you're criticizing the article and talking about percentages, you're addressing the wrong point.
still quite meaningless when making a purchasing decision based on the range of the vehicle. Here:
500 gallons at 2MPG, 200 gallons at 5MPG.
Gee I saved 300 gallons! (Even though I only get 3 more miles per gallon, it must be the best option! I'm saving the most!)
Well, the idea is that if you have a vehicle that gets 5MPG or whatever, probably a more efficient vehicle that does the same job (i.e. SUV or minivan) probably isn't going to get more than 10-20MPG.
But then, in that case, I don't know why it would matter. Either you're replacing an SUV with another SUV or you're replacing a small car with another small car - and it doesn't matter which of the two options saves more fuel, because which one you replace depends on which one you have...
The only scenario I can think of where the article's complaint maybe makes sense is if a family had an inefficient SUV and a relatively inefficient small car, and could only replace one for financial reasons, and had to pick which one. Then which of the two options would save the most fuel? That seems to me the only case where inverting the ratio is really helpful. You can say, OK, using 100 gallons per 1000 miles now on the SUV, could switch to 50 gallons per 1000 miles for a new SUV, or replace my 30 gallons per 1000 miles compact with a 20 gallons per 1000 miles compact... That makes the difference clear. Even though replacing the compact gives you a greater difference in MPG (17 vs. 10), replacing the SUV would result in greater overall fuel savings. Of course, a better comparison would also include how much you drive one vehicle vs. how much you drive the other...
Bow-ties are cool.
Measuring fuel consumption in units of volume burned per distance isn't a fair measure of fuel efficiency. Your diesel vehicle is given the appearance of being more fuel efficient than the equivalent gasoline vehicle in these units because diesel fuel is far denser than gasoline.
A more honest comparison would be to compare fuel efficiency in kg/100km. The mass of fuel burned correlates more closely with the amount of CO2 produced, for example, than it does to the volume.
Diesel fuel has a mass of about 850 g/L, compared to gasoline at about 720 g/L. To compare diesel to gasoline fuel consumption you can approximate this difference by dividing the diesel volume/distance numbers by 1.18.
The underlying assumption (miles per year and $/gallon) are both printed on the label.
They are going to be consistent for all vehicles in the same class and the same model year, so in the most common cases of comparisons, the variations won't matter. Its true that they are situations where the variations need to be accounted for.
Its fairly trivial one-time calculation to convert your existing cars rating (presuming you got a car from a model year after the EPA adopted the current methodology) to correct it to the gas price used on labels for the current model year (just multiply the total estimated cost from your cars rating by the the new labels stated cost per gallon and divide by your labels cost per gallon; you've then got a number you can use when comparing against any car from the current model year.)
Of course, if you want to know the actual cost savings, you'll need to correct for the actual mileage you tend to drive each year, rather than the standard mileage estimate (you probably also want to adjust the gas cost estimate by the usual ratio of gas cost in your market as compared to the national average.)
Getting to these actual cost numbers starting with a gallons per mile figure, of course, is no easy task, either.
> last March
Last March? Or this March?? Which is it? *sigh*
Flying cars? Velocity? Would those be European or African Flying cars?
Agent K: A *person* is smart. People are dumb, stupid, panicky animals, and you know it.
The choice for an Hybrid or a fuel efficient car should not only take in to account the cost of the fuel, but also the cost to the environment. If you add the cost of a "carbon fee" for the extra fuel you burn, for the energy required to bring that fuel to you, the damage to the environment to extract that fuel, you get quite a good deal...
No, you get a CRAPPY deal, and the rest of the inhabitants of the planet get a tiny, tiny, tiny better deal.
And that's being very, very, very optimistic.
The reason hybrids cost more to buy than standard engines is that they COST MORE TO MAKE. And cost is a very good indicator of environmental impact. Sure, over the course of the lifetime of the car, a lot of money is spent moving the fuel to the car, extracting the fuel, a very large portion of that is already reflected in the cost of the fuel. Just like building a hybrid engine itself has an environmental impact - building a hybrid engine causes MORE damage to the environment than building a simple conventional engine. All that lithium in the battery pack in the Prius has to be mined from somewhere.
In the vast majority of cases, the CHEAPEST option is also the most environmentally sound option, because use of resources has a cost. About the only place this doesn't hold true is emissions, but even then things like gas have taxes much higher than things like food, so in most cases the gas tax more than covers the extra environmental impact consuming gas has over consuming, say, corn.
Long story short: If the gas engine car is cheaper, buy that one.
paintball
Why should I care if I get more bang for the buck from going from 10 mpg to 20 mpg vs. going from 33 mpg to 50 mpg? What I care about at the end is how much I'm going to spend going from car #1 to car #2. And, I imagine the vast majority of people care about that.
As long as I can calculate cost per tank on car #1 vs. car #2 then I can plan a budget accordingly. I think most people care more about that.
The underlying assumption (miles per year and $/gallon) are both printed on the label.
They are going to be consistent for all vehicles in the same class and the same model year, so in the most common cases of comparisons, the variations won't matter.
But that's not the point. This article was pretty clearly talking about a situation where a 2 car family is trying to figure out which of their 2 cars is going to be the most beneficial to upgrade. For that to happen, you are going to need to know the figures for your existing vehicle.
Its a fairly trivial one-time calculation to convert your existing cars rating (presuming you got a car from a model year after the EPA adopted the current methodology) to correct it to the gas price used on labels for the current model year (just multiply the total estimated cost from your cars rating by the the new labels stated cost per gallon and divide by your labels cost per gallon; you've then got a number you can use when comparing against any car from the current model year.)
LOL...yeah, right. You are talking about the same people who can NOT figure out whether 10->20 will save you more than 33->50, and now you expect that they are going to be able to make this calculation on their own?
Of course, this is all a moot point because (as others have already pointed out) it is very rarely financially advantageous to replace an old car with a new one. If you keep your old car and spend X dollars extra on gas (compared to the car you would have bought) and spent Y dollars in upkeep, X+Y will generally be less than the financed cost of the new vehicle minus the residual value of that new vehicle. So, for most people, it really only makes sense to replace a vehicle when it no longer suits your needs (it has become too unreliable, is not safe, does not meet your new family needs or your cargo needs, etc).
And even if we go with the fact that the family is probably not smart enough to realize this and will thus upgrade one of the vehicle anyway, we still need to know the ratio of usage between the 2 vehicle.
But if we kind of put these 2 problems aside and just discuss within the premise of the article (no matter how faulty), then "annual fuel cost" figures are no simpler for people to correctly analyze than the MPG figures are.
Yes, and the figures you are going to need to know are the actual fuel costs of your current vehicles and the expected fuel costs of the new vehicles. Neither gallons per mile nor the existing label gets you there without a bunch of other calculations, though if you have good records of actual costs and mileage on the existing cars, it will be a step or two shorter if you start with gallons/mi on the label, true.
OTOH, for lots of other common comparison use case, especially for comparing new cars against each other, the est. $/year is more useful. (And, for people who don't keep extensive records of their own, the est. $/year would continue to be more useful if the EPA also kept -- say, on the web -- the ratings for older vehicles updated to the assumptions used for newer vehicles.)
Gallons/mile is only useful superior to the est. $/year -- or even mpg -- for meaningful comparisons when you use other information and do calculations based on it, not as a direct comparator. And if you are willing to do that kind of calculation, its a simple calculation to derive gallons per mile from mpg.
If they can't do the calculation on their own, they can't make a meaningful comparison in the precise use case you refer to unless you further assume that the usage patterns for the two cars are identical, which is typically not the case in two-car families. After all, fuel economy doesn't tell you which saves more gas without considering the usage pattern.
But, after reading that website, apparently I'm not really saving much from one to the other.
About 1.3 cents per mile by my calculation (and Google’s) – assuming gas costs $2.599, which is a bit higher than I paid for it this morning. That’s about a quarter (26 cents or so) for a 20-mile commute... and you save about 5:49 of driving time.
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
I'm a bit miffed by the current measuring system we use here in Europe, with liters per 100km. Seems a rather arbitrary and cumbersome, and I've always wondered why we don't just use liters per megameter instead. Go from 4.7 l/100km to 47 l/Mm. Metric and SI FTW! :)