The 2008 models already in many dealers’ showrooms sport a redesigned fuel economy sticker on their rear windows. But the U.S. Environmental Protection Agency (EPA) has revised more than merely the look of the stickers. It has also changed the methodology used to estimate mpg, resulting in lower, more realistic estimates.

Under the old methods, the agency calculated its estimates based on drives not faster than 60 mph in pleasant weather, using no air conditioning. Under the new methods, the agency accounts for situations such as cold-weather starting, running the air conditioner in 95-degree heat and accelerating hard to 80 mph.

On average, the new methods have resulted in an 8 percent decrease in estimated highway mpg and a 12 percent drop in estimated city mpg.

AAA has applauded the new methodology, calling it a  “truth-in-advertising issue.” “Armed with better information, consumers can make informed choices,” says Robert L. Darbelnet, president of AAA national. “AAA intends to monitor developments in EPA testing and the government’s progress in implementing this much needed change.”

Two years ago, AAA tests revealed wide discrepancies between real-world fuel economy and EPA estimates. These tests provided some of the impetus for EPA’s updating its methods.

Aside from lower numbers, you’ll notice other changes on the new sticker. They include a more prominent location for the estimated annual fuel cost (in bold numbers in the center of the sticker) and an easy-to-read scale, showing how the vehicle’s combined city-highway mileage compares with that of others in its class.