The WardsAuto Fuel Economy Index reached a record 24.6 mpg (9.6 L/100 km) in August, up 2.7% from year-ago and 17.2% from the base rating of fourth-quarter 2007.

The new monthly benchmark comes as both cars and light trucks set record index ratings. The four most fuel-efficient segments, currently at 25.9 mpg (9.1 L/100 km) and higher, all held or surpassed their highest scores to date.

Cars recorded a 28.2 mpg (8.4 L/100 km) FEI, up 3.8% from like-2012 and 17.7% from the base index. Small cars, the most fuel-efficient segment, reached 30 mpg (7.8 L/100 km). Midsize cars maintained their highest score of 28.6 mpg (8.2 L/100 km) reached in July.

Luxury cars saw the largest FEI gain in August, reaching 25.9 mpg (9.1 L/100 km), up 10.6% from prior-year and 29.9% better than the segment’s 2007 base score. The improvement was the result of an increase in hybrid and electric powertrains.

The only car segment to see a slight drop from the July FEI was large cars, at 21 mpg (11.2 L/100 km). However, with a mere 1.6% share, the index was not significantly impacted.

Light trucks achieved a 20.4 mpg (11.5 L/100 km) FEI, up 1.7% from like-2012 and 14.5% from 2007. The boost was driven by cross/utility vehicles, which rose slightly to 22.5 mpg (10.5 L/100 km), the highest ever. CUVs account for nearly half of light-trucks sales, and their share continues to grow.

Domestic light vehicles reached a record as well, up to 23.8 mpg (9.9 L/100 km) in August. Cars reached a new high of 28.2 mpg (8.3 L/100 km), and light trucks peaked at 19.8 mpg (11.9 L/100 km).

Volkswagen remained the top auto maker on the August FEI (excluding all-electric Tesla), with a record 28.2 mpg (8.4 L/100 km). The auto maker continues to see growth of its diesel model sales, which are averaging 33.5 mpg (7 L/100 km).

Ford earned the biggest gain in August compared with year-ago, up 7.4% to 23.6 mpg (10 L/100 km). The auto maker’s hybrid sales rose 3.2% from 1.1% in like-2012. Ford introduced its first battery-electric and plug-in hybrid models in 2012.

The WardsAuto Fuel Economy Index through the year’s first eight months rose 1.9% from year-ago to 24.4 mpg (9.7 L/100 km).

eberger@wardsauto.com