New EPA Rules for 2008 Models

Nov. 17, 2006: Chicago Tribune—Road to More Accurate Mileage

Summary: "Since the federal government began estimating the fuel economy of new vehicles 33 years ago, it’s been careful to note that actual mileage may vary. And how, say motorists who don’t get the mileage that appears on the window sticker.

The U.S. Environmental Protection Agency hopes to curb such complaints in early December when it announces new rules for calculating its estimates. They’ll be rolled out beginning on 2008 model year cars.

Though the new procedures are expected to reduce the estimates from 5 percent to 25 percent, the agency’s boilerplate warning will still apply: Your mileage will vary."

Currently, corporate average fuel economy (CAFE) standards are used to impose fines on automakers that don’t meet fuel efficiency targets.

EPA’s new measurement method will result in lower, more realistic mileage numbers for all vehicles. Will those new numbers be used to calculate an automaker’s CAFE?

If so, look for a scramble toward E85 flex-fuel powertrains. A special rule allows vehicles with such powertrains to fake extra efficiency—even if E85 never touches the car’s gas tank.


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  • Bill

    I have driven many different types of cars, and except for my 2000 New VW Beetle 2.0, I got better than the EPA ratings. I currently have a 2005 Honda Civic Hybrid and get the EPA ratings or better depending on the A/C in the summer (I live in AZ). I never had an issue with the ratings before, since I always made or exceeded them. Maybe now, when a huge SUV rated at 14 mpg is show as 7 people will wake up. Regardless what the EPA rates it, I will get my information from true users and only buy hybrids.

  • Richard

    these new ratings may really dampen hybrid demand. Having the civic and prius in the high thirties for Hwy, is a huge difference from 50. And the % knocks way more acual mpg from the hybrids than it does an SUV.

  • C Durnell

    I think the key to this issue–as Walter McManus pointed out earlier this year–is to look at how much gasoline a car consumes over a given distance, not the mpg. If you look at the inverse proportionality function ‘gallons/mile = 1/mpg’ (or to make the magnitude relevant ‘gallons/(100 miles) = 100 * 1/mpg’) it’s asymptotic to the ‘x = mpg’ axis so that large changes in mpg as you get closer to the 100 mpg limit effect negligible change in gallons/100 miles. However, as you get closer to 10 mpg the effect is pronounced. For instance, EPA’s current and proposed 5-cycle combined fuel economy numbers for the Prius are 54.6 and 45.9 mpg respectively. This results in a change from 1.83 to 2.18 gallons/100 miles, or 0.35 gallons/100 miles. At the other end of the spectrum, EPA’s numbers for current and 5-cycle combined fuel economy for a Chevy Silverado 4WD were 16.9 and 14.9 mpg respectively, or from 5.92 to 6.71 gallons/100 miles, which is a change of 0.794 gallons/100 miles.

    Clearly, the new EPA 5-cycle method FAVORS hybrids. The problem is in how the data is presented.

  • Brian

    Mr(s) Durnell,

    You are right, the problem is in how you present the data. In your example, the Prius’ consumption increased by 19% whereas the truck’s consumption increased by 13%. Doesn’t look like this favors hybrids from this angle does it?

    If they want real mileage, why not put trip computers in the cars and have RF stations read consumption, average mileage and current mileage along with the VIN. Then we could have meaningful statistics, not irrelevant simulations.