The average fuel economy (window-sticker value) of new vehicles sold in the US in August 2017 was 25.3 mpg (9.29 l/100 km)—down 0.1 mpg from July, according to the latest monthly report from Dr. Michael Sivak and Brandon Schoettle at the University of Michigan Transportation Research Institute (UMTRI). The value for August is up 5.2 mpg since October 2007 (the first month of their monitoring), but still down 0.2 mpg from the peak of 25.5 mpg reached in August 2014.
The University of Michigan Eco-Driving Index (EDI)—an index that estimates the average monthly emissions of greenhouse gases generated by an individual US driver—worsened to 0.83 in June 2017, up from 0.82 in May 2017 (the lower the value, the better). The EDI indicates that the average new-vehicle driver produced 17% lower emissions in June 2017 than in October 2007, but 5% higher emissions than the record low reached in November 2013.
The EDI takes into account both vehicle fuel economy and distance driven (the latter relying on data that are published with a two-month lag).