The WardsAuto Fuel Economy Index for U.S. light-vehicle sales reached a record-high 25.3 mpg (9.3 L/100 km) in March, marking a 2.2% gain on year-ago and a 21.0% improvement from the fourth-quarter 2007 base score.

The rating for cars was an all-time high 29.4 mpg (8.0 L/100 km). Increased market share of small cars, which have held steady at 30.9 mpg (7.6 L/100 km) for four months, along with a drop in the share of large cars (23.0 mpg [10.2 L/100 km]) moved the average upward.

Light trucks averaged 21.1 mpg (11.1 L/100 km), falling slightly from February. Despite that decline, the March light-truck score was 3.4% above same-month 2013.

Even though light trucks still dominated the market, increased market share of cars compared to prior-month helped the index reach the new high.

The shift toward smaller vehicles also elevated Ford (24.5 mpg [9.6 L/100 km]) and General Motors (23.3 mpg [10.1 L/100 km]) to record results.

The score for Asian automakers was bumped to an all-time high of 27.4 mpg (8.6 L/100 km) by Mazda’s and Nissan’s new records. Mazda remained the top company (excluding electric-only Tesla), reaching 29.4 mpg (8.0 L/100 km). Nissan averaged 28.4 mpg (8.3 L/100 km), up 2.2% from the prior month and 2.5% from year-ago.

European automakers also had a new high at 24.4 mpg (9.6 L/100 km), boosted by Volkswagen and Jaguar Land Rover. Volkswagen was the most improved company from last month, up 2.8%, hitting a record 28.3 mpg (8.3 L/100 km). A significant factor in that increase was a jump in the sales of diesel-powered vehicles, which averaged 33.8 mpg (7.0 L/100 km).

JLR has shown significant growth each of the last seven months, up to 19.8 mpg (11.9 L/100 km) in March. As this trend continues, the automaker likely will surpass 20 mpg (11.8 L/100 km) within the next couple months. JLR has been the only company below that benchmark since August 2012.

Domestically built vehicles averaged 24.8 mpg (9.5 L/100 km), and imports scored 27.3 mpg (8.6 L/100 km).

National gasoline prices rose to an average $3.60 a gallon, resulting in the fourth consecutive monthly increase.

Market share of electric, hybrid and diesel-powered vehicles increased from February in March.

Year-to-date, the WardsAuto FEI averaged 25.3 mpg (9.3 L/100 km), up 2.2% from the same period last year.

eberger@wardsauto.com