Even with SUV and crossover utility vehicles sales surging, the average fuel efficiency of new vehicles sold in August set a new high for the U.S., according to a new report.
Overall, the mileage for new cars and trucks averaged 24.9 MPG, according to Michael Sivak with the University of Michigan.
"I am not surprised that overall fuel economy is improving," says Sivak, who has been tracking fuel efficiency for the last six years. "Buyers are selecting more fuel-efficient vehicles within each class of vehicles."
With the sales of 2013 model year vehicles winding down as automakers transition to 2014 models, the University of Michigan calculates the average fuel economy of model year '13 vehicles sold from October 2012 through last month is 24.7 mpg.
That's up 1.2 mpg from model year '12 vehicles.
SUV sales surging
Nearly one out of every three vehicles sold last month was an SUV or crossover utility vehicle. All told, the group saw sales jump 24.1 percent, well above the industry increase of 17 percent.
Despite that difference, Sivak says the overall fuel economy average moved higher because even large vehicles are going further on a gallon of gas.
"The SUV's and crossovers being sold now are much more fuel efficient than even a few years ago," said Sivak.
At the same time, there has been an uptick in sales of gas-electric hybrid vehicles and electric vehicles, which have also helped raise the average fuel economy.
(Read more: Electric car future 'definitely coming,' Lutz says)
Five years ago, the average fuel economy of new vehicles sold in the U.S. was 20.8 MPG. Since then it has risen 19.7 percent.
Sivak says the trajectory from here is for the average fuel economy to keep climbing, especially as more 2014 models with higher MPG roll into showrooms.
"I do expect the average to pass 25 MPG this month or next," said Sivak.
—By CNBC's Phil LeBeau. Follow him on Twitter @LeBeauCarNews.
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