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EPA Fuel Economy Myth: Too High, Too Low?
ThosLives asks: "I have seen here on Slashdot , and just about every other publication, numerous articles about fuel cells, hybrid vehicles, and the inaccuracies of EPA fuel economy stickers. For instance, today there is a review of the Toyota Prius that had the famous line 'Since no car really achieves the EPA estimated mileage...' I happen to drive a car with an EPA sticker of 21 city 25 highway (all figures in miles per gallon). I've driven the car for 47000 miles and the lowest I've ever seen is 23 and some change; the highest, 36.3 (I'm probably about 60% highway 40% stop-and-go and yes, the high was on a long highway trip). My all-time average is about 28.5. As most people get less than the EPA mileage, how does the Slashdot readership fare when it comes to EPA sticker vs actual experience, and on what type of vehicle?"
"Am I a rare breed that can drive my car (2.0L I4, 170 HP, 6-speed manual) aggressively (I've had coworkers and friends say 'woah!' more than I'd like to admit *grin*) and still stomp the EPA sticker? Did I get lucky with a phenomenal car? Am I enough of a counter-example to thwart the belief that the EPA figures are 'too liberal'? Are fuel economy issues just FUD from [insert lobby group of choice]? Or is the answer simply 'it depends on how you drive, what you had for breakfast, and the color of your neighbors' cat?'"
Car: Audi TT(6spd 225HP 1.8L turbocharged sports coupe). EPA: 20/28. Actual average for a tank has ranged from a low of 24mpg to a high of 33mpg. The 24mpg is a fairly even mix of city and highway driving. That value seems to correspond pretty closely to what one would expect from the EPA numbers. The 33mpg is all highway, of course, in sixth gear, with no turbo.
http://www.fueleconomy.gov/
When the weather is warm, and that seems to be the biggest factor, I get the EPA-rated 70 mpg or more in my 2000 Honda Insight. 55 on cold winter days.
Driving at moderate speeds is also a big factor.
It's really a quick and a smart thing to do and I encourage everybody to do it. Your fuel economy will be one of the first warning signs that your car is developing a problem. If that drops it's time to take the car to get looked at. Just a little time to save major money on repairs later. And if you go to sell your car you have a record of its health.
If not now, when?
and everyone's mileage DOES vary.
I own a 2004 Prius, and I must say that I DON'T get the mileage advertised, although I have seen per-trip variations outside what I so-far consider my normal range. My own figures are closer to 47MPG (combined) for the life of the car, now at 4000 miles. However, my style of driving tends to be shorter trips taken in a hilly locale--both of which negatively influence mileage. Slightly longer trips (a daily commute of 60+ miles) and flatter terrain (coming north to town on the coastal plain) allows a friend here (also with an '04 Prius) to average 53 or so. All other factors seem similar--we have similar driving styles, same tires at same pressure, etc.--but there's a big difference in the mileage figures for the same car. I don't think the EPA takes this into account; they're looking at a bad extrapolation of data based on emissions and a short test--almost a perfect, no-wind, flat-land drive.
I believe the Prius is a good, capable machine. I can see how, in the right circumstances, the car would do as well as, or better than, the EPA figures. Lots of folks do it.
Check out Greenhybrid.com and Prius Chat and see what others have to say.
What'dya mean there's no BLINK tag!?
My '03 Hybrid Civic had (I think) 48/47 on the sticker. When I drive it, the "MPG" meter in the dashboard ends up around 42-46. At the pump, I actually get 39-44.
-- I prefer the term "karma escort."
In cold weather the Prius got between 35-40. Now that the weather is nice, I've been getting 48-52 for my commute. My wife who does more short trips and sits at lights with the AC on gets quite a bit less. The first 5 minutes in the Prius is very poor (about 25) as it is agressive in maintaining the engine coolant temprature for the low emissions. If it was designed for millage instead of emissions, it could do a lot better. Where the car does a fantastic job is in stop and crawl driving if you are not using the AC. It does that with the engine off 90% of the time. Conventional cars don't fare nearly as well as you are stopped too short to shut off the engine and sitting idling is zero MPG. An extra bonus is the car doesn't overheat in those conditions like my old car did. A warm day and stop and crawl traffic would usualy result in some loss of coolant.
The truth shall set you free!
My 90 ZR-1 was stickered at 16/25. I got 18 city, and from 27 (80mph) to 33 (65mph). Not too shabby for 375 hp.
:)
Its replacement, a 2004 Z06, is stickered at 19/28 and I'm seeing 18.5/33-35 quite respectable and 405 hp to boot.
I love it when some econo-box criticizes my sports car as a gas guzzler and finds out I get better milage than they are
The first thing we do, let's kill all the lawyers. Shakespeare, Henry VI, Part 2, Act 4, Scene 2
Yes, this is obvious since it's the whole point of a hybrid like the prius. It takes less energy to drive slow (like in city driving). And you loose your energy in city driving from all the stop and go and idling at stops. A prius doesn't waste power idling, and gains the power back when braking. So it will get better mileage city, thats the whole idea. Hybrids don't do well on highway driving do to energy losses. For driving down the highway a conventional drivetrain is best. When it comes to high mileage on mildhybrids like the insight it's because it's light and areodynamic, not because it's a hybrid.
That's not exactly true.
Have you seen my stapler?
Higher compression engines, or more highly-tuned engines, need higher octane gas. Mostly, it's to prevent knocking (early detonation caused by compression rather than spark). Any good car of relatively recent make (at least the past 10 years, if not older) will have a knock sensor to adjust for lower-octane gas, at the expense of fuel usage. However, if your car is designed to run on 87 octane, higher test gas shouldn't make much of a difference.
Actually, there is less energy potential per gallon in higher octane gas than lower. That's not really an issue, though. What most likely happened was that previously you were not using the proper octane-level gas for your engine's compression and the ECM was adjusting to a less optimal program to compensate. As a side note, race gas and airplane gas have much higher octane ratings due to the use of lead additives. Don't try this in your car. Lead will kill your cats in a matter of minutes, not days or months. Race cars and airplanes don't have catalytic converters.
First off, most additives are snake oil. Pretty much the only thing that works is Techron (and knock-off brands using a similar formulation). If you fill your car at a station with Techron or a similar cleaning additive, there's no reason why you should have to add injector cleaner on your own. If you must, an application once or twice a year is sufficient. Any more often and you're just throwing money away. As for better gas giving you better mileage, that's true up to a point. As I mentioned already, higher compression engines require higher octane fuels. If you're not using the right fuel, your engine will operate inefficiently. Using a higher octane gas than is required is useless if your car can't adjust its compression ratios to make use of it (ie, putting 92 octane gas in a low compression engine like many American-made engines isn't going to help anything, while putting 87 octane in a high compression Porsche engine is going to give you poor performance and mileage). If it's bad gas you're worried about, the most common problem is too much water in the gasoline. You can solve this problem with an alcohol additive to "dry" the gas. Other problems like too much sulfur (I believe that was the problem recently with some gas down in Florida, among other places) don't have an easy remedy, and all you can do is stop driving, have the car towed, and empty the tank. Run a few tanks of good gas through the engine and it'll be fine.
As others have already stated in this article, there are many other factors to consider. Low tire pressure, dirty air filter, oil, oil filter, bad alignment, too much weight (of the driver, passengers, and any cargo), etc will all have an effect on your mileage. Also, most cars will get their best mileage at low RPMs. If you can cruise at 2000RPM, you're going to get much better mileage than cruising at 5000RPM (just be careful -- you're going to be in a high gear to cruise at such a low RPM, and trying to accelerate in that gear could cause you to lug your engine. This is more important in high-revving, low-torque engines than it is in low-revving, high-torque engines).
Links:
I'm riding a Honda Rebel around town now. The car I replaced with the bike was a 1992 Toyota Corolla that pegged in at about 30 MPG on the highway and 21 on the city streets. Since most of my driving was city streets, I'd have to fill up every week or less, depending on the travel schedule. The cost of gasoline now would make my average trip to the station about cost between $25 and $50 per week, again depending on how many times I needed more gas.
I've had the bike for about 2 months now, and I think I reached $50 total in gas this weekend. I haven't figured out the total mileage yet; when the tripmeter reaches 150 miles, I get paranoid that I'll have to cut in the reserve (2.1 gallons in the primary, .6 in the reserve) so I fill up. I always go in and put $5 on the counter, fill up the bike, and go back and get my change. I'm guessing that I'm hovering around 80 MPG.
And I'm getting a tan while I run errands.
There's so little difference between politics and jihad lately...
"Supreme", "92 octane", "premium", whatever you call it- is not *better*. It has a higher octane rating. Oddly, that just means that it's more difficult to ignite it.
If you're getting better gas mileage with it, that means your engine is probably suffering from pre-ignition, aka "pinging", without it. It doesn't mean the higher octane gas has more energy, just that you don't have a cylinder or two working against the rest of the engine. I used to have a jeep that was terrible with pinging unless I used 92 octane, so I am familiar with the situation.
But for most cars, the 87 is just fine. Note that the 92 doesn't have more cleaners or anything else in it. For the vast majority of cars, 87 works fine and there is no reason to get ass-raped by the filling station for 92 octane. It's like shoe size: a size 13 shoe isn't "better" than a size 8, unless your feet are size 13. If your feet are size 8, however, the size 13 doesn't offer you anything more.
The FTC has considered regulating the oil industry by disallowing any terminology suggesting that higher octane is better.
The Low-Down on High Octane Gasoline
Do you have ESP?
Well, come on, I use 15l/100km, and that's driving a European vehicle. Driving a heavy SUV and carting around heavy stuff all the time talkes fuel.
Note that US gallons (3.6l) are different from imeperial gallons (4.5l), so that can lead to some confusion between UK and US posters!
MW
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BDOS ERR ON A:>
However, heavy lobbying (GM, C and Ford) managed to get defense contractors and other contractors, landscapers included in the scheme.
In the late eighties creative accountants started to include ordinary companies like small entrepenurs and got IRS approval for this. When the SUV market exploded in the nineties it became common for everyone with a small company (dentists, doctors etc) to get the tax break.
It's allways possibly to debate what came first; the tax break or the SUV (as an evolution from the truck and the station wagon)?
I think the SUV would have appeared sooner or later as an evoutionary thing within car industry but it would never had gotten so widespread without the tax break. And the truck segment would have been far far smaller than today.
The tax break is a protectionistic piece of shit mutated far from the original concept without any thought of the consequences, be it environmental, energy policy or foreign policy. If someone where to write a book on how special interest is allowed to corrupt US policy on several areas the SUV tax break case is a perfect example.
And BTW to the root poster that brought up this topic: The tax break is far greater than $4000. According to Taxpayers for common sence it's possible get tax break around $100000. They site an example where a business owner can buy a $110000 Hummer and deduct $106000.
Melius mori in libertate quam vivere in servitute.
Current: Ford F150 5.4L V8, I average 19mpg with a heavy focus on highway driving and light emphasis on difficult offroad or towing duties (live in a very rural area). It does OK and beats the sticker mpg mpg by 2. Towing heavy loads in the 5000-7000lb range, mpg drops to roughly 10mpg which is bad. My next truck will have to be a diesel. Ironically, my car in highschool and college was a 1.8L Diesel VW Rabbit with extended fuel tank. It averaged 60mpg and with the extra fuel tank I could fill it up at the start of summer and not need to refill to school started in the fall. Fuel economy has been solved way back in the day, sadly no one in the US wants diesels.