September U.S. Fuel Economy Index Up 2.1%

New light vehicles sold in the U.S. in September averaged 25.1 mpg (9.4 L/100 km), up 2.1% from same-month 2013 and 20.0% better than the base score of fourth-quarter 2007, according to the WardsAuto Fuel Economy Index.

BMW posted a record 28.2 mpg (8.3 L/100 km) in September. The i3 electric vehicle and i8 plug-in were major factors in BMW’s high rating, but the automaker also saw the biggest month-to-month gain of diesel vehicle sales this year. BMW’s diesel cars (35.5 mpg [6.6 L/100 km]) rate higher than their gasoline-powered cars (26.7 mpg [8.8 L/100 km]) by more than any other automaker.

The result for cars was up 3.2% from last year to 29.5 mpg (8.0 L/100 km). Small cars reached an all-time high 31.2 mpg (7.5 L/100 km), and luxury cars hit a record 26.7 mpg (8.8 L/100 km). Increased EV sales boosted both segments.

Light trucks held the 2014 average of 21.1 mpg (11.2 L/100 km). After maintaining a rating of 17.7 mpg (13.3 L/100 km) through the first eight months of this year, pickups ticked up to a high of 17.8 mpg (13.2 L/100 km) in September. Although pickup sales have shifted to heavier models in the second half of this year, increased popularity of diesel models has kept the average index rating up.

The national average gasoline price in September was $3.484, resulting in a third consecutive month-to-month drop. The market share of gas-powered models in September was at its highest point since February, when prices were slightly less.

Diesel prices averaged $3.792 in September, the lowest for any month this year. The share of diesel-powered vehicles on the index reached the highest monthly result of 2014.

The September outcome matched the average for the index’s model-year 2014 models. A score of 25.1 mpg (9.4 L/100 km) for October 2013 through September 2014 was 2.2% higher than the same period a year ago.

Diesel was the only fuel-type to see a drop in average fuel economy for the model year, down 1.1%. The decline was not due to lower efficiency of individual models, but an increase in the market share of trucks over cars. The gain in diesel LV share, from 2.1% to 2.3%, came primarily from light trucks. Diesel-powered light trucks reached 23.0 mpg (10.2 L/100 km), up 0.9% from model year 2013. Diesel cars held steady at 0.7% of the LV market and 33.6 mpg (7.0 L/100 km) on the index.

The score for gasoline-powered LVs also was pulled down by increased truck share. The overall score for this category was 24.0 mpg (9.8 L/100 km) for model-year 2014, up 2.3%. However, the score for cars grew 2.6% to 27.3 mpg (8.6 L/100 km), and light trucks were up 3.0% to 21.0 mpg (11.2 L/100 km).

The only power-type to lose market share of indexed LV sales was hybrids, which dropped to 2.9% from 3.3%. Hybrid models averaged 44.2 mpg (5.3 L/100 km) this model year, up just 0.4% year-over-year.

On the other hand, electric and plug-in hybrid models posted significant gains over the model year. New battery and motor technology improved the eMPG of electric vehicles 3.9%, and lessening range anxiety increased sales share 30%. Share of PHEVs was up 21%, though MPG rose only 0.6%.

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