ANN ARBOR—Gas mileage of new vehicles sold in the U.S. dropped for the third straight month in October and is now at its lowest mark since September 2013, say researchers at the University of Michigan Transportation Research Institute.

The average fuel economy (window-sticker value) of new vehicles sold last month was 24.8 mpg—down 0.4 from September and the first time in nearly three years that it has fallen below 25 mpg.

“However, this likely reflects not only a continuing increase in the proportion of light trucks sold each month, but also the recent calculation adjustments for window-sticker values implemented by the EPA for model year 2017,” said UMTRI research professor Michael Sivak.

Overall, fuel economy is down 1.0 mpg from the peak reached in August 2014, but still up 4.7 mpg from October 2007—the first full month of monitoring by Sivak and colleague 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 August, the EDI improved to 0.81 (the lower the value, the better) from a mark of 0.82 in July. The index currently shows emissions of greenhouse gases per driver of newly purchased vehicles are down 19 percent, overall, since October 2007—but 3 percentage points higher than the record low reached in both August 2014 and August 2015.

More informaton: 

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

U-M Sustainability fosters a more sustainable world through collaborations across campus and beyond aimed at educating students, generating new knowledge, and minimizing our environmental footprint. Learn more at sustainability.umich.edu.