DETROIT (AP) —  New cars and trucks in the U.S. got a record 24.1 miles per gallon on average last year, but the rate of improvement is slowing as buyers shift back toward trucks and SUVs.

The Environmental Protection Agency says fuel economy rose one-half mile per gallon over 2012, mainly because automakers have improved gas engines and transmissions and added turbochargers to give smaller motors more power.

But last year’s gain fell short of the 1.2 mpg improvement from 2011 to 2012. And the EPA is predicting smaller growth for 2014. Still, fuel economy is up almost 5 mpg since 2004.

Mazda led all automakers with an average of 28.1 mpg. Chrysler, General Motors and Ford were at the bottom of the rankings because they sell more pickups and SUVs.