According to a monthly report by Michael Sivak and Brandon Schoettle from the University of Michigan, the average fuel economy of newly purchased vehicles declined during the month of April.

The average fuel-economy (window-sticker) value of new vehicles sold in the U.S. in May was 24.8 mpg. This value is unchanged from the revised value for April, and it is up 4.7 mpg since October 2007 (the first month of our monitoring). For a description of the calculations and the recent mpg values, click here.

The University of Michigan Eco-Driving Index (EDI)--an index that estimates the average monthly emissions of greenhouse gases generated by an individual U.S. driver--stood at 0.81 in March (the lower the value the better). This value indicates an improvement of 19% since October 2007. 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). Please click here for a brief description of what the EDI is, how it is calculated, and the current and recent values of the EDI.

According to GasBuddy, the national average has risen slightly over the last month and currently stands at $3.635 per gallon, up from last month's average of $3.60.

With gasoline prices rising in areas of the country, it is possible that next month's reading shows a new record high of new vehicle fuel economy.