In the wake of the Hyundai/Kia MPG issue, sources say that the Environmental Protection Agency, the lead U.S. government institution responsible for the MPG (miles per gallon) figures, will be looking to audit more figures from more manufacturers, according to a senior EPA engineer.

Last year, Hyundai and Kia compensated customers regarding significant discrepancies over EPA fuel economy ratings from real world consumption. Currently, Ford is being sued by a California man for not getting the advertised 47 mpg as rated on his C-Max hybrid.

The EPA computes the MPG ratings (1 mile per gallon = 0.425 kilometers per liter) with the car strapped to a dynamometer (dyno, rolling road) while an engineer drives at specific speeds at any given second. Lab equipment then measures the exhaust gases expended (specifically carbon) by the vehicle to come up with a consumption figure, a method more accurate than using a fuel gauge or similar meter.

Take note that the fuel economy estimate issued by the EPA does not take into account real world variables like but not limited to drag, weight, traffic, air density and ambient temperature. Also, given the methods for testing, hybrids, EVs and other alternative fuel vehicles are tricky to give EPA mileage estimates to.

“Everybody wants a label that tells you exactly what you’re going to get, but obviously that’s not possible,” said Jeff Alson of the EPA. “A good general rule of thumb is that real-world fuel economy is about 20 percent lower than the lab numbers.”

The audit is in line with the Obama administration's proposal for increased fuel economy standards by 2025, wherein fuel economy targets will be raised to 54.5 mpg.