Fuel economy of new vehicles sold in the U.S. set another record high last month, say researchers at the University of Michigan Transportation Research Institute.

Average fuel economy (window-sticker values) of cars, , vans and SUVs purchased in May was 25.6 mpg, up 0.4 mpg from April and 0.2 from March—the previous high. Vehicle fuel economy is now up 5.5 from October 2007, the first full month of monitoring by UMTRI researchers Michael Sivak and Brandon Schoettle.

"This increase likely reflects the continuing high price of gasoline," Sivak said.

In addition to average , 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.

The EDI stood at 0.78 (the lower the value, the better) during March, up slightly from February's record-low 0.77 in February. The index currently shows emissions of greenhouse gases per driver of newly purchased vehicles are now down 22 percent, overall, since October 2007.

More information: Fuel economy calculations, along with a graph and table of current and recent mpg: www.umich.edu/~umtriswt/EDI_sa … es-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