For the fifth straight month, the average fuel economy for new vehicles sold in the U.S. remained above 25 miles per gallon.
The average in June, weighted for sales, was 25.5 mpg, down slightly from 25.6 mpg in May, according to a monthly report by the Transportation Research Institute at the University of Michigan.
That average is 27 percent higher since October 2007, when the institute began recording fleet-fuel-economy numbers.
However, automakers face a federal fuel-economy requirement of 54.5 mpg by model year 2025.
Two years after that requirement was imposed, average fuel economy has increased about 2 mpg, and even that modest gain has not been consistent.
In January, the average was 24.9 mpg, and while the average has remained above 25 since then, it fell slightly in April and June.
Typically, if monthly truck sales increase more rapidly than car sales, the average fuel economy will decrease a bit.