Sales-weighted fuel economy slips in June

The average fuel economy in newly sold vehicles in the United States fell back in June, according to researchers at the University of Michigan Transportation Research Institute.

The typical vehicle sold during the month had a combined fuel economy of 25.1 miles per gallon. This was down from 25.3 miles per gallon in May and 25.2 miles per gallon in June 2016.

The decline marked the first drop in sales-weighted fuel economy since February. The figure had matched or improved upon the previous month's average in the three months prior to June.

UMTRI researchers Michael Sivak and Brandon Schoettle have been tracking fuel economy in new vehicle sales since October 2007. In that month, the average vehicle sold in the U.S. got 20.1 miles per gallon. The figure is calculated using monthly sales data as well as fuel economy information on specific vehicle models from the Environmental Protection Agency.

The average sales-weighted fuel economy reached a high of 25.5 miles per gallon in August 2014. Since then, it has wavered between 24.8 miles per gallon and 25.3 miles per gallon. The model year average, or average fuel economy for the months between October and September, has held at 25.1 miles per gallon for three consecutive years.

The researchers also calculate a figure known as the Eco-Driving Index, which measures the estimated level of emissions generated by a driver of a typical newly purchased vehicle against those of a comparable driver in October 2007. This index is updated on a two-month delay due to a corresponding lag in data updates from the Federal Highway Administration.

The Eco-Driving Index for April stood at 0.84, indicating that the typical driver of a new vehicle was generating emissions levels that were 16 percent lower than the baseline. This was unchanged from the previous year, but marked the first time since August that the index has improved from the previous month. The lowest Eco-Driving Index, 0.78, was recorded in November 2013.

For the third month in a row, the distance driven in the United States was 5 percent higher than in October 2007. The fuel used per distance driven in April was 20 percent lower than the baseline figure.