New-vehicle fuel economy has now fallen for three straight months and is down from a high of 25.8 mpg last August. UMTRI also tracked new-vehicle emissions for July and found they were four percent higher than last August.
Some of the country's best-selling plug-ins, including the Chevrolet Volt extended-range plug-in and the Nissan Leaf battery-electric, are about to come out with upgraded versions. That's spurred a wait-and-see attitude in new-car buyers that in September helped drive green-car numbers down about four percent from a year earlier. This contributed to the lower fuel-economy numbers. Last month, green car sales fared relatively well compared to the rest of 2015, especially given that Volkswagen's diesel scandal helped cause a plunge in that automaker's September sales. Year-to-date green car sales across the US are down about 16 percent in 2015.
Additionally, UMTRI says falling gas prices were also a factor. Americans on average are paying $2.29 a gallon, which is down from $2.41 from a month ago and marks a plunge from the $3.30 folks were paying a year ago, according to AAA's Fuel Gauge Report.