The average fuel economy of U.S. new light vehicles sold in April reached 25.1 mpg (9.4 L/100 km) according to the WardsAuto Fuel Economy Index, a 20.9% improvement over the fourth-quarter 2007 baseline and a 1.6% gain on April 2013.

(Note: The WardsAuto Fuel Economy Index was recalibrated this month with additional engine installation and sales information. The current and past scores referred to in this story and the accompanying table reflect those changes.)

The index rating for cars held steady from the prior month at 29.2 mpg (8.1 L/100 km). Increased share of large cars was balanced by improved sales of alternative-power vehicles.

Light trucks averaged 21.0 mpg (11.2 L/100 km), resulting in the third monthly down-tick in a row. CUVs, the most fuel-efficient light-truck segment, saw a decline in both market share and index score. The other segments in this category maintained last month’s ratings.

The average score for the Detroit Three, which accounted for 45.4% of U.S. LV sales, fell 1.0% from March. General Motors (22.6 mpg [10.4 L/100 km]) had the biggest decline of the three, dropping 1.6%, and had the greatest impact on the industry average with an 18.6% market share. Ford’s 24.0 mpg (9.8 L/100 km) average, down 0.8%, was 13.9% of the indexed market.  Chrysler’s index score (20.9 mpg [11.2 L/100 km]) and market share (12.9%) were nearly equal to the previous month.

Asian automakers accounted for 45.7% of the market, but their 0.1% month-to-month improvement in index score was not enough to counter the Detroit Three’s impact. The average for Asian automakers was raised to a new high of 27.4 mpg (8.6 L/100 km) by record scores for Mazda, Honda and Nissan.

Mazda remained the top automaker with a 29.7 mpg (7.9 L/100 km) rating. An 11.5% gain on last year came from increased popularity of its small and midsize cars over CUVs.

Honda’s share of cars and light trucks held steady from the prior month, but the segment mix within cars shifted to smaller vehicles in April. Adding increased share of alternatively fueled cars, the automaker averaged 26.9 mpg (8.7 L/110 km).

Nissan, coming in at 28.7 mpg (8.2 L/100 km), beat last month’s score through increased hybrid and electric vehicle sales.

Volkswagen also ticked up to a new best-ever score in April, reaching 28.4 mpg (8.3 L/100 km) due partly to a gain in the share of diesel-powered vehicles over gasoline.

The only manufacturer to post a significant decline from last year was Kia, falling 4.4% to 25.4 mpg (9.3 L/100 km).

The national average gasoline price rose for the fifth consecutive month, reaching $3.74 per gallon in April. Despite a 3.6% increase in fuel prices from last month, sales of gasoline-powered vehicles fell less than 0.1%.

Through the first four months of the year, the WardsAuto Fuel Economy Index sits at 25.1 mpg (9.4 L/100 km).

eberger@wardsauto.com