ANN ARBOR—The average fuel economy of new vehicles sold in the U.S. last month remained unchanged at 25.3 mpg, say researchers at the University of Michigan Transportation Research Institute.

The value for September is up 5.2 mpg since October 2007—the first full month of monitoring by UMTRI researchers Michael Sivak and Brandon Schoettle—but still down 0.2 mpg from the peak of 25.5 mpg reached in August 2014.

For model year 2017 vehicles (sold October 2016 through September 2017), the average fuel economy was 25.2 mpg, up slightly from 25.1 mpg for each of the preceding three model years.

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 0.81 (the lower the value, the better)—down from 0.83 the month before. 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 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