New-vehicle fuel economy in the US fell last month from a record high in August and was at its lowest level since January, likely reflecting a drop-off in sales of hybrid models such as the Toyota Prius, the University of Michigan's Transportation Research Institute (UMTRI) reports. September's fleetwide fuel economy came in at 24.6 miles per gallon, down from a record 24.9 mpg in August. Year-over-year figures were still up from 23.8 mpg in September 2012.

The drop jibes with green-car sales figures that have started tapering off as well as declining gas prices. Average gas prices are at about $3.37 a gallon, down from about $3.55 a gallon as of early August, according to AAA. Meanwhile, US sales of hybrids, plug-ins and diesels in September fell 1.8 percent from a year earlier to 46,523 units and were down 36 percent from August.

Of course, some of that decline is attributable to the fact that Labor Day was counted in August this year but in September last year. Still, demand for the Prius, which had surged earlier in the year, appears to be waning a tad as sales for the model's four variants collectively fell 16 percent from September 2012. Check out UMTRI's press release here and data here.

Share This Photo X