—The U.S. Environmental Protection Agency said Wednesday that German automaker Daimler AG will lower the miles per gallon estimates on two of its Mercedes-Benz vehicles after a government audit turned up a problem.

Mercedes-Benz will make minor changes to two models. It will reduce the city mpg figure for the 2013-14 C300 to 19 mpg from 20 mpg, but the combined 22 mpg and 27 mpg highway value will remain the same. For the 2013-14 4-Matic PZEV the combined mpg fell to 23 mpg from 22 mpg, while the city and highway mpg figures both fell by 1 mpg to 19 and 28, respectively. The 1 mpg restatement only impacts about 500 cars, Mercedes-Benz said.

The EPA said the issue was discovered during fuel economy audit testing. "With EPA oversight, Mercedes conducted new emissions and fuel economy testing, and EPA conducted its own testing at its National Vehicle and Fuel Emissions Laboratory in Ann Arbor," the agency said.

The adjustment is minor compared to some other automakers that have made significant restatements of fuel economy values.

"Even though the adjustments are small, it is important that our oversight system is producing the correct results because even one MPG matters to consumers," said Christopher Grundler, director of EPA's Office of Transportation and Air Quality. "EPA will continue strong oversight of fuel economy values to ensure that consumers have the best information available to make important purchasing decisions, to ensure fair competition among automakers, and to protect investments in new fuel efficient technologies.

Mercedes-Benz spokeswoman Donna Boland said "as a German company we place a high value on precision, even we miss the mark once in a while." She noted just two of the "out of the over 70 Mercedes-Benz models being off by 1 mpg. We will revise fuel economy label for that particular model" that was replaced by a new generation C-Class in August.

The original mpg figures reported by Mercedes underestimated the impact of aerodynamic drag and tire rolling resistance known as "road-load," the EPA said. While this error impacted the fuel economy estimates by a small amount, these vehicles were found to be in compliance with emissions standards.

EPA said it also tested several other Mercedes as part of this spot check, and found the labels were accurate.

In June, Ford Motor Co. said it is lowering the fuel economy ratings on six new cars, including the combined city/highway rating on the Lincoln MKZ hybrid by 7 miles per gallon, and would make payments of $125 to $1,050 to more than 200,000 owners as compensation for the extra money drivers will spend on gas because of lower-than-promised fuel efficiency.

EPA said Ford reported the mistakes after an internal audit. Ford will lower fuel-efficiency estimates on four versions of the 2014 Fiesta subcompact; the hybrid and Energi plug-in hybrid versions of the 2013 and 2014 Fusion midsize sedan; the C-Max Hybrid and Energi plug-in hybrid version; and the Lincoln MKZ Hybrid. Ford must correct the window labels within 15 days.

The move is a significant embarrassment to Ford, which has emphasized the fuel efficiency of vehicles in its lineup. And it's the second time in a year that Ford has had to correct its mileage numbers.

Ford had heavily touted the fact that eight of its 2013 models got 40 mpg or better. The revisions mean three of the eight don't make that number: The Lincoln MKZ fell from a combined 45 mpg to 38 mpg; the C Max Energi plug-in hybrid and Fusion Energi plug-in hybrid fell to 38 mpg from 43 mpg, and the all-electric range of those models dropped to 19 miles from 21 miles.

This is the second time in less than a year that Ford has restated fuel efficiency of its vehicles. In August 2013, it dropped the fuel economy rating on the 2013 C-Max Hybrid from a combined 47 mpg to 43 mpg — a nearly 10 percent reduction — and said it would compensate owners for the worse-than-promised fuel economy. That restatement affected 32,000 customers.

Ford isn't the only other automaker whose fuel mileage claims have been too high. In November 2012, Hyundai and Kia Motors — two Korean automakers controlled by the same conglomerate — admitted overstating mileage on nearly 1.1 million vehicles in North America sold since 2010, including about 900,000 in the United States. The automakers set aside about $400 million to compensate drivers for the mileage difference and to resolve lawsuits filed by buyers.

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