Vehicle fuel economy stays the same in July

(Phys.org) -- After a three-month drop, fuel economy of all new vehicles sold in the United States remained unchanged in July, say researchers at the University of Michigan Transportation Research Institute.

Average fuel economy (window-sticker values) of cars, light trucks, minivans and SUVs purchased last month was 23.6 mpg, a 17 percent increase (3.5 mpg) from October 2007, the first month of monitoring by UMTRI researchers Michael Sivak and Brandon Schoettle.

In addition to average fuel economy, Sivak and Schoettle issued their 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 vehicle fuel economy and distance driven—the latter relying on data that are published with a two-month lag.

During May, the EDI stood at 0.82, up from 0.81 in April (the lower the value, the better). The index currently shows that emissions of greenhouse gases per driver of newly purchased vehicles are down 18 percent, overall, since October 2007.

Finally, Sivak and Schoettle report the unadjusted Corporate Average Fuel Economy performance. This index is based on a different set of EPA ratings than window-sticker values.

For July, unadjusted CAFE performance was 29 mpg, the same as in June and an increase of 17 percent (4.3 mpg) since October 2007.