There are miles per gallon... and then there are miles per gallon. How do you tell the difference? One is labeled "CAFE mpg" and the other is labeled "EPA mpg." What's the difference? Well, Edmunds is taking pains to illuminate the large discrepancy that exists between the two figures: the issue, as initially laid out by Edmunds' John O'Dell in 2007, is that CAFE and EPA mileage numbers were initially based on the same formula in 1975. When consumers complained that the number didn't correspond to real-world gas mileage, the EPA determination formula was changed – twice – yet the CAFE formula wasn't.

The change meant that when a customer bought a car that listed 26 combined mpg (EPA) on the window sticker, the CAFE mpg rating for that car remained at around 35 mpg. And if you've been paying attention to the myriad CAFE stories over the past year, you'll know that the government is tweaking CAFE numbers, not EPA numbers. The NHTSA oversees CAFE numbers, the EPA keeps track of "vehicle fuel efficiency."

But the gap between the two sets of computations means, according to Edmunds:
"a vehicle that scores an EPA combined rating of 29 miles per gallon actually contributes 39 MPG to its manufacturer's CAFE average. There are 29 car models and 36 truck models that already achieve the new standard, and about a third of the cars and half of the trucks are produced by a domestic automaker."
Ultimately, it means that the formerly punitive mpg numbers that the government mandated can now be considered for what they really are: Meh. You can read Edmunds' full press release after the jump.

[Source: Edmunds]

PRESS RELEASE

Edmunds.com Discovers CAFE Discrepancy; New Goals Not What They Seem

SANTA MONICA, Calif. -- Even supporters of CAFE might be surprised to learn that the standards announced this week will actually require automakers to make much less progress than implied.


"Turns out that there are loopholes almost big enough to drive an SUV through," quipped Edmunds.com CEO Jeremy Anwyl to AutoObserver.com.

One might think the government would use a single set of ratings for both CAFE and vehicle window stickers. But the well-known EPA mileage ratings are not used to calculate CAFE, and the difference can be significant. For example, a vehicle that scores an EPA combined rating of 29 miles per gallon actually contributes 39 MPG to its manufacturer's CAFE average. There are 29 car models and 36 truck models that already achieve the new standard, and about a third of the cars and half of the trucks are produced by a domestic automaker.

Edmunds.com Director of Vehicle Testing Dan Edmunds explained, "CAFE miles per gallon ratings and EPA window sticker MPG ratings were originally generated simultaneously through government lab testing. Window sticker ratings have been downrated twice in the last 25 years to make them more realistic for consumers, while CAFE mpg methods remained the same. So, with each EPA revision, EPA window sticker MPG and CAFE MPG drifted further apart."

Edmunds' GreenCarAdvisor.com Editor John O'Dell originally reported on this discrepancy in December 2007, in an article entitled Fuel Economy: Doublespeak at its Best (at http://blogs.edmunds.com/greencaradvisor/2007/12/fuel-economy-doublespeak-at-its-best.html.) In that piece, he wrote, "Most people have been trained to think only of the EPA numbers when talk turns to fuel economy, and they aren't aware of the differences between the EPA and CAFE figures. That makes the standard a little misleading."

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