Average light-vehicle fuel economy reached a record 24.5 mpg (9.6 L/100 km) on the WardsAuto Fuel Economy Index in July, up 2.9% from year-ago and 16.8% from the base rating set in fourth-quarter 2007.

Light-truck market share grew in the month, but any downward effect on miles per gallon was offset by increased FEI scores for both cars and trucks as sales skewed toward more-efficient models.

Cars set a record of 28.4 mpg (8.3 L/100 km) in July, a 4.6% increase from like-2012, as buyers gravitated to smaller models more so than in June. Small cars maintained their highest FEI score (29.9 mpg [7.9 L/100 km]), and midsize cars regained their previous high (28.5 mpg [8.3 L/100 km]) from late 2012.

Large cars also reached a new peak at 21.1 mpg (11.1 L/100 km).

The rating for domestic cars also represents a new high of 28.2 mpg (8.3 L/100 km), up 5.7% from last year. However, sales shifted more toward imports, which made up 30.2% of car sales while earning an FEI score of 28.9 mpg (8.1 L/100 km) for July.

The light-truck FEI tally reached an all-time high of 20.4 mpg (11.5 L/100 km) in the month, primarily a result of cross/utility vehicle demand. The best-selling vehicle group, CUVs made up 50.3% of light-truck deliveries and 25.7% of all LV volume, while reaching a segment-record 22.5 mpg (10.5 L/100 km).

Also influencing the light-truck performance was a small market shift toward imports, which posted a new high of 23.3 mpg (10.1 L/100 km).

All auto makers exceeding the market average on the WardsAuto FEI also gained market share from June.

Volkswagen had its best month at 28 mpg (8.4 L/100 km) in July, a 4.5% improvement from year-ago. It led all auto makers (excluding single-model-seller Tesla) for the second consecutive month, as its share of hybrid- and diesel-car sales increased.

Hybrids accounted for 1.7% of VW sales, up a full point from year-ago, and averaged 44.8 mpg (5.3 L/100 km) compared with 25.3 mpg (9.3 L/100 km) for the brand’s gasoline-powered models.

More significantly, diesel models, which averaged 33.4 mpg (7 L/100 km), made up 29.9% of VW LV volume in July, compared with 24.3% in June and only 19.4% year-ago.

To date, the WardsAuto Fuel Economy Index stands at 24.4 mpg (9.6 L/100 km), a 1.8% gain from like-2012 and up 16.4% from the index base figure.