How the EPA calculates gas mileage

[ehallman]

I invite all to watch the video at: http://video.staged.com/localshops/vw_passat_785_mpg_in_the_uk

After watching it, then comment on the validity of what is presented.

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[yarddog1950]

Everything he says is flawed. Where to start? US gallons are about 20% smaller than Euro/British gallons. Simply put, that VW diesel will not get anywhere near 70 mpg on a US gallon.
You would think this could be simple. After all, if you need to convert US dollars to Pounds or Euros, you just google the current exchange rate and do the math. If you drive a car in one place and imagine driving it in another, you can expect to get the same mileage out of a gallon if the gallon is of the same size. You can compare identical cars with identical drivers with identical gallons. You can compare EPA figures with other EPA figures because EPA tests are identical for similar cars. I’ve looked at mpg figures for cars from Europe and I’ve seen how they differ from the same cars sold here in the US. They don’t compare. Sometimes the difference is about 20%. Sometimes the difference is higher or lower. Not at all like exchanging currencies.

So this fellow is angry that he can’t buy a dirty diesel here. I think reasonable people would be content with our cleaner diesels if they knew how little mpg difference there is between them.

[ehallman]

I have to agree with yarddog1950, but the question remains. The EPA might want to justify their reason for being. They talk about how bad fuels are dirty per gallon consumed. They measure the fuel fouling per gallon of fuel burned, but do not take into consideration how many miles you go on that gallon or liter or pint or tablespoon full. I suspect we have been mislead for reasons that have nothing to do with green miles or pollution, but a government desk job looking for job security. If they can make you believe it, then their retirement with full benefits are in sight. That was the purpose of posting the link. The guy might have been off, but the point was made to me.

[yarddog1950]

If you watch that fellow’s video on YouTube, you find a link he provides that claims the German VW diesel will get over 70 mpg in US gallons. They say this was demonstrated for a Guinness World Record. Does Guinness allow the “techniques” used by Mpg competitions like coasting with the engine turned off, crawling up to speed, and almost never using brakes? I’ve read that these competitions yield huge Mpg gains. You have to be a wee bit wacko to do that sort of thing.
http://www.vehix.com/blog/most-popular/fuel-efficient/vw-tdi-drives-1531-miles-on-one-tank

[yarddog1950]

http://www.snopes.com/politics/business/passat.asp

Snopes.com says that the VW blue motion diesel gets mid forties mpg on US gallons. The article is short and very informative.
Snopes says there are cars that sell in Europe and not here because people over there will buy something like the Passat Blue Motion which does 0 to 60 in 12.5 seconds. Over here, people will trash mouth cars that do 0 to 60 in 10 seconds. Consider the new US Fiat 500. It does 0 to 60 in about 10 seconds and will get 42 mpg according to Consumer Reports, 39.5 mpg according to Edmunds and 38 mpg according to the EPA. Yet there are reviews that complain about slow acceleration. Fiat announced plans to sell the 133 hp turbo version of the 500 here in the US to improve acceleration. The 500 Abarth Turbo goes on sale here soon and that has 160 hp. But Fiat says they will not sell the 500 “twin-air” 2 cylinder in the US because Americans won’t buy it in sufficient numbers. The 500 Twin-Air is very popular in Europe and is capable of great mileage.
I think that poor fellow who made that video probably knows almost nothing about engines or diesel or the EPA or politics or even English and German pronunciation. Volkswagen is pronounced “Vokes wagon” and there’s no fur in familiar.
He also assumes the diesel VW is is EPA tested for emissions on a per gallon basis. I think the EPA tests for emissions on a per mile basis. Is diesel given a fair shake by the EPA. I’m not sure. I have read a lot about how they test and it seems obvious they make every effort to be fair and accurate, but there are difficulties comparing automatics to manuals, hybrids to conventional cars, and there a few cars like the Fiat 500 that score higher in real world tests than the EPA lab tests because the Fiat (and others) use unusual technology.

[yarddog1950]

[url=http://www.edmunds.com/fuel-economy/fuel-sipper-smackdown-4-which-car-gets-the-best-fuel-economy.html:3llmqi0f]http://www.edmunds.com/fuel-economy/fuel-sipper-smackdown-4-which-car-gets-the-best-fuel-economy.html

I[/url] think this comparison test is one of the best sources of info about what a VW diesel will do in the real world. This is not Bluemotion VW, but realize the difference is a smaller less powerful engine, an alternator that de-couples and little else. BlueMotion is not any advanced diesel technology exclusive to VW. I think the BlueMotion VW might have some trouble keeping up with the other green cars tested. Out of five green cars, three are impressive and they take unusual technological approaches to high mpg. The Chevy Volt gets the best mpg. It’s expensive but it’s also a desirable car for many purposes. The VW diesel got great mileage and pleased most of the drivers. The Fiat 500 is out of its element here on a long road trip. It’s supposed to be a “city car”. The Fiat has a gasoline engine with the most advanced electronic variable valve timing on the road and low end torque that permits low rpm cruising like a diesel. It can exceed the EPA estimates and the other cars in the test don’t meet them.
The Hyundai and Kia come in behind the others.
My question is which technology would you like to see in next years cars? Fiat’s “MultiAir” might be the winner over the Volt’s hybrid technology when you look at the initial and long term expense of the two technologies. And what of diesel engines versus MultiAir. The mpg is close. The fuel cost is higher for diesel and so is the initial cost. The diesel is probably at a disadvantage when it come to power and emissions too, but Fiat says they are working MultiAir for diesels. It’s a real possibility. After all, Fiat developed Common Rail Fuel Injection, the one huge improvement in diesel technology, now owned by Bosch and in use on everybody’s diesel engines.

[ehallman]

yarddog1950 you are good. But the question remains unanswered. The subject is: How the EPA calculates gas mileage. So give me a little help here. Remember I am a newbee and a dumb old south Georgia country boy. Most of us good ole boys seem to fall short of the mark of excellence when it comes to technical stuff.

[yarddog1950]

[url=http://www.caranddriver.com/features/the-truth-about-epa-city-highway-mpg-estimates:3vugndbd]http://www.caranddriver.com/features/the-truth-about-epa-city-highway-mpg-estimates
I[/url] read a number of articles about your question through a Google search, and this one seems to be the best. It’s 4 pages but the subject is at least that complicated and there are surprising facts on every page.
For instance, in comparing EPA figures versus European figures for “highway” mileage, the testing is very different and the EPA comes up with much lower numbers. A vehicle rated at 60mpg by European authorities, would score in the mid forties on the EPA Highway tests.

[ehallman]

yarddog1950 you are still good. I visited the webpage you suggested and almost went blind reading it. The article clearly explains how good technicians get rapped up in test that do not seem to prove out across the board. Over the years the EPA has done these test, what is proven? I can only suggest that the approach is wrong and there has to be a better simpler way to solve fuel mileage problems. It appears to me that they have run off on a tangent that needs to be refocused. What is the purpose of this division of the EPA? For the public, across the board: You want good fuel mileage, govern the throttle. If you have a heavy foot, then rely on the government protect you from yourself. Restrict the weight to horsepower. Ask the question, how much fuel does it require to move “x” number of people from a starting point to the destination and for what reason. I am one of those who believe that fuel should be priced close to the the price of gold per the same weight of gold. Somebody needs to wake up. I had the same problem growing up of thinking I was ten feet tall and bullet proof. Now that I am in my 60’s I have finally began to educate myself.

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