The average fuel economy of new vehicles sold in the US. in January was 23.0 mpg US (10.2 L/100 km), an increase of 0.8 mpg from December, according to figures from the University of Michigan Transportation Research Institute (UMTRI).
UMTRI’s Eco-Driving Index (EDI)—an index that estimates the average monthly emissions generated by an individual US driver—stood at 0.86 in November 2011 (a decrease of 14% from October 2007). The EDI takes into account both vehicle fuel economy and distance driven (the latter relying on data that are published with a two-month lag).
The average sales-weighted fuel economy was calculated from the monthly sales of individual models of light-duty vehicles (cars, SUVs, vans, and pickup trucks) and the EPA “combined” fuel-economy ratings for the respective models. All vehicles purchased from October 2007 through September 2008 were assumed to be model year 2008. Analogous assumptions were made for vehicles purchased in each additional model year. The fuel-economy information was available for 99.8% of vehicles purchased.
For cases in which the EPA fuel economy guide contained multiple fuel-economy values for a vehicle model, the average of these values was used (without regard to sales figures for each specific engine or vehicle-model variant). Additionally, when a vehicle model was sold during a particular model year but it is not listed in that year’s EPA fuel economy guide, the fuel economy value(s) from the most recently available year were used. Finally, for very low sales-volume manufacturers (e.g., Ferrari, Rolls-Royce, etc.), all vehicle models for that manufacturer were aggregated and one average fuel-economy value was calculated. Analogously, the sales figures for such manufacturers and models were also aggregated each month.