Automakers had their fourth consecutive year of outperforming federal greenhouse gas reduction requirements in 2015.

The Environmental Protection Agency and National Highway Traffic Safety Administration’s greenhouse gas (GHG) emission standards were met by nine out of 12 automakers that sold more than 150,000 cars in the U.S. last year. These nine automakers exceeded the standard by an average of seven grams per mile for the 2015 model year.

Nissan and Subaru had the strongest numbers for outperforming GHG standards by 23 grams per mile each. FCA, Mercedes, and Kia each fell behind the standard. For the three automakers lagging behind the emissions standard, FCA came closest but missed the mark by three grams per mile, Mercedes was behind by 11 grams per mile, and Kia trailed behind by 12 grams per mile.

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Corporate average fuel economy for automakers rose to 24.8 miles per gallon for the 2015 model year. That made for an increase of 0.5 mpg from 2014.

Last year saw a tightening of the gap in emissions reduction. In 2012, automakers passed the market by 11 grams per mile, with the figure topping out in 2014 at 13 grams per mile. As the GHG requirements increase in years ahead, it’s expected to only get tougher for automakers to meet or beat the federal standards.