ANN ARBOR—Gas mileage of new vehicles sold in the U.S. reached an all-time high in August, but slipped to its lowest mark in nine months during September, say researchers at the University of Michigan Transportation Research Institute.

Average fuel economy (window-sticker values) of cars, light trucks, vans and SUVs purchased in August was 24.6 mpg—down 0.3 mpg from August, according to UMTRI researchers Michael Sivak and Brandon Schoettle. However, gas mileage is up 4.5 mpg overall since October 2007, the first month of monitoring.

“The decline likely reflects the recent reduction in the price of gasoline,” Sivak said.

The average fuel economy of model year 2013 vehicles (vehicles sold October 2012 through September 2013) was 24.7 mpg. This is up 1.2 mpg from model year 2012 vehicles.

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 July, the EDI improved to 0.80—tying its best mark ever set late last year (the lower the value, the better). The index currently shows that emissions of greenhouse gases per driver of newly purchased vehicles are down 20 percent, overall, since October 2007.

Related Links:

• Fuel economy calculations, along with a graph and table of current and recent mpg: www.umich.edu/~umtriswt/EDI_sales-weighted-mpg.html
• Eco-Driving Index calculations, along with a graph and table of current and recent values: www.umich.edu/~umtriswt/EDI_values.html

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.