ANN ARBOR—Gas mileage of new vehicles in the U.S. dropped in June, say researchers at the University of Michigan Transportation Research Institute.

The average fuel economy (window-sticker value) of new vehicles sold last month was 25.1 mpg—down 0.2 mpg from May.

“This drop likely reflects the decreased price of gasoline in June, and the consequent increased proportion of pickup trucks, SUVs and crossovers in the sales mix,” said Michael Sivak, research professor at UMTRI.

Overall, fuel economy is down 0.4 mpg from the peak of 25.5 mpg reached in August 2014, but still up by 5.0 mpg since October 2007—the first full month of monitoring by Sivak and Brandon Schoettle.

In addition to average fuel economy, Sivak and Schoettle issued a monthly update of their national Eco-Driving Index, which estimates the average monthly emissions generated by an individual U.S. driver. The EDI takes into account both the fuel used per distance driven and the amount of driving—the latter relying on data that are published with a two-month lag.

During April, the EDI improved to 0.84 (the lower the value, the better)—down from 0.85 the month before. The index currently shows emissions of greenhouse gases per driver of newly purchased vehicles are down 16 percent, overall, since October 2007—but 6 percentage points higher than the record low reached in November 2013.

More information:

• Fuel economy (with graph and table of current/recent mpg)
• Eco-Driving Index (with graph and table of current/recent values)
• Related research
• Michael Sivak
• Brandon Schoettle