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 June.

The average fuel-economy (window-sticker) value of new vehicles sold in the U.S. in June was 24.7 mpg--down 0.1 mpg from May. This slight reduction likely reflects the recent drop in the price of gasoline. However, the fuel economy is up 4.6 mpg since October 2007 (the first month of monitoring). For a description of the calculations and the recent mpg values, click here.

The average fuel economy of model year 2013 vehicles sold thus far (October 2012 through June 2013) is 24.6 mpg. This is up 1.1 mpg from model year 2012 vehicles.

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 0.82 in April (the lower the value the better). This value indicates an improvement of 18% 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 in June was slightly lower than it was in May, which may contribute to the slight drop in fuel economy of new vehicles. Americans tend to buy less fuel efficient vehicles when gasoline prices are low. The average pump price in May according to GasBuddy was $3.61 per gallon, while prices in June averaged $3.60 per gallon.