Photo via Wikpedia.

Photo via Wikpedia.

The average fuel economy of new vehicles sold in the U.S. in September fell 0.5 mpg to 25.3 mpg from August — a significant drop attributed to increased sales of light trucks and SUVs, according to research from the University of Michigan.

The data comes from the university's Transportation Research Institute, which releases monthly reports tracking the average EPA-rated fuel economy from newly sold vehicles. The monthly report is produced by Michael Sivak and Brandon Schoettle.

Even with the drop, fuel economy has increased 5.2 mpg since October 2007 when the institute began tracking window-sticker fuel economy.

The University of Michigan's Eco-Driving Index (EDI) — an index that estimates the average monthly emissions of greenhouse gases generated by an individual U.S. driver — stood at a record low of 0.77 in July (the lower the value the better). This value indicates that the average new-vehicle driver produced 23 percent lower emissions in July than in October 2007, according to the institute.