WASHINGTON, DC -- On Tuesday, Jan. 10, the U.S. Environmental Protection Agency (EPA) announced plans to update its fuel economy testing, thereby giving a more accurate estimate of miles per gallon on vehicle window stickers.

According to The New York Times, the EPA proposal is the first major overhaul in 20 years in the way the agency calculates fuel economy ratings for cars and trucks, which would “reduce mileage estimates by 5 to 30 percent, depending on the type of driving and kind of vehicle.” EPA expects the new changes to apply to model year 2008 vehicles, which will generally be for sale in the fall of 2007.

EPA Administrator Stephen Johnson told the Times that the proposed standards are meant to more accurately report on window stickers what consumers can expect in terms of miles per gallon when they purchase a new car or truck.

“With President Bush encouraging energy conservation, EPA is ensuring American motorists can be confident that the fuel economy estimates more closely reflect today's real-world driving experiences,” Johnson said in a press release.

EPA notes that the new calculations will have the greatest impact on hybrid-electric vehicles, which are powered by a gasoline engine and an electric battery. The agency’s new testing methods, writes the Times, could produce a 10 to 20 percent drop in fuel economy estimates for all vehicles in city driving, and a 5 to 15 percent reduction in highway driving. For hybrids, city driving estimates could drop 20 to 30 percent, but the highway driving estimates would remain the same as regular cars.

The EPA also states in a release that none of the changes proposed would affect the Corporate Average Fuel Economy (CAFE) program, which is administered by the U.S. Department of Transportation. “There are separate requirements for the test methods and procedures for determining fuel economy values under CAFE,” says the EPA.

The EPA’s proposed fuel economy testing standards are open to public comment for 60 days. Click here to view the proposal and information about how to submit comments.