The Environmental Protection Agency wants to put automakers’ mileage claims to the test.
The EPA is considering a proposal that would require automakers to road test vehicles to verify mileage claims before they are posted on window sticker prices and other sources.
The agency said all automakers would be required to perform what it calls "in-use auditing."
"At this early stage, it is premature for us to speculate on what form a proposal may take," the agency said in a statement. "EPA will engage interested stakeholders proactively before making any proposal."
The development was first reported by The Wall Street Journal.
The move follows the recent restatement of EPA ratings on several cars and light trucks by Hyundai, Kia and Ford.
It's part of a broader effort by the agency to more carefully scrutinize mpg figures published by automakers.
The agency said any proposed rule would be subject to a public notice, comment and rulemaking process.
The difference between a driver’s actual mileage and what a vehicle is rated is among the most frequent consumer complaints and questions posed to the agency.
“Some automakers already do this, but we are establishing a regulatory requirement for all automakers,” Chris Grundler, director of the EPA’s Office of Transportation and Air Quality, told The Journal.
The proposal also would make it difficult for automakers to manipulate lab results to deliver higher mileage claims, the paper said.
Ford amended mileage estimates on several hybrids last month, while Hyundai is being sued by consumers in South Korea over accusations it overstated the fuel efficiency of the Santa Fe crossover.
In 2012, Hyundai and affiliate Kia apologized and compensated owners for overstating mileage estimates on light-vehicle models sold in the United States.
At Ford, the recent mileage claims were based on poor testing conditions and faulty engineering practices, including wind tunnel and other laboratory measurements.
The EPA, as The Journal noted, does not evaluate every new light-vehicle to verify mileage claims. Most fuel economy tests are performed by automakers, and the information is later shared with and reviewed by the agency.
The data is also published on the agency’s public Web site, www.fueleconomy.gov.
The EPA last adjusted fuel efficiency testing in 2008, which narrowed the gap between window sticker numbers and what owners experienced in real-world driving.
The proposed road test would make real-world driving trials more rigorous and reflect air resistance and rolling friction on a test track rather than in a test lab, The Journal reported.
These factors can affect fuel economy considerably, especially in hybrids.