Fuel economy of new vehicles sold in the U.S. is now at an all-time high, say researchers at the University of Michigan Transportation Research Institute.

Average (window-sticker values) of cars, , vans and SUVs purchased in August was 25.8 , up 0.2 mpg from July. Vehicle fuel economy is now up 5.7 mpg from October 2007, the first full month of monitoring by UMTRI researchers Michael Sivak and 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 June, the EDI improved to a record-tying 0.78 (the lower the value, the better), down from 0.79 in May. This was the fifth time it had reached its record low in the last year. The index currently shows emissions of greenhouse gases per driver of newly purchased vehicles are now down 22 percent, overall, since October 2007.