The Environmental Protection Agency will recommend that automakers be required to perform additional road testing to confirm the fuel-economy claims posted on their vehicles, rather than relying on laboratory measurements.
The Wall Street Journal reported last week that the EPA proposal comes after recent cases where some mileage estimates from Ford Motor Co., Hyundai Motor Co., and Kia Motors Co. turned out to be overstated.
The EPA wants automakers to measure vehicles' air resistance and rolling friction on a test track rather than rely on computer modeling, according to the Journal.
Chris Grundler, director of the EPA's Office of Transportation and Air Quality, told the Journal that some companies already do this kind of testing, "but we are establishing a regulatory requirement for all automakers."
Changes made to the testing in 2008 have helped make the numbers more closely align with what consumers can expect, but there are still some inconsistencies, the Journal said. Its own analysis has found that hybrids tend to underperform lab results while diesel engines often do much better than their posted numbers.
AAA issued a statement lauding the EPA proposal.
"For most Americans, a new vehicle is the second largest investment they will make and it's imperative they have accurate information to inform their purchase," the statement says. "While reports show that many consumers actually experience better fuel economy than promised, it is important for the ratings to be as accurate as possible and not overstate real-world performance."
Before the EPA can take action on the proposal, a public comment period is required.