Mercedes-Benz is lowering fuel economy estimates for the 2013-'14 C300 and the 2013-'14 4-Matic PZEV after the EPA discovered that their miles per gallon estimates were slightly overstated.

The EPA tested both compact sedans to find that their fuel economy estimates were inflated by 1 mile per gallon in city driving, Reuters reported. The automaker had given each model a rating of 20 mpg, but EPA tests rated the cars at 19 mpg in city driving.

The PZEV was initially rated at 29 mpg on the highway by Mercedes-Benz, but regulators found that the sedan got an estimated 28 mpg for highway driving.

The EPA noticed the discrepancy while testing during a fuel economy audit. Other Mercedes vehicles were tested as well and found to have accurate fuel economy ratings.

The agency is requiring Mercedes-Benz to relabel the C300 all-wheel drive models affected by the new mpg rating.

Mercedes has stated that only around 500 vehicles are affected by the 1 mpg restatement, according to the News.

"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, as quoted by the Detroit News.

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