Slowly Climbing the Fuel-Efficiency StaircaseThe University of Michigan's Transportation Research Institute keeps track of the average fuel economy of new vehicles sold in the United States. It's a bit depressing to see how slowly things are progressing, but at least there is some progress; it would be even more depressing to see a decline in MPG over time... The noteworthy milestone that was reached last month is an average of 24.1 MPG, the first time ever that the MPG average for new vehicles in the U.S. has been above 24 MPG.
As you can notice on the graph above, so far the 2012 average is 23.4 MPG, but recent months have spiked quite a bit, most probably thanks to higher fuel costs.
If you are curious about the methodology, here's what the authors of the study had to say:
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 combined city/highway fuel-economy ratings published in the EPA Fuel Economy Guide (i.e., window sticker ratings) for the respective models. For both monthly and model year averages, sales-weighted means were calculated. The bars in the graph show the average for each model year. 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 ratings for a vehicle model, the average of these ratings 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 rating(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 rating was calculated. Analogously, the sales figures for such manufacturers and models were also aggregated each month. (source)
Still, no car can beat walking or biking, and only plug-in vehicles can come close to transit. Only drive if you have to, and pick the most fuel-efficient vehicle that meets your needs.