U.S. light-vehicle fuel-efficiency fell for the first time in four months in April but still registered the second-highest monthly rating ever on the WardsAuto Fuel Economy Index.

New cars and light trucks sold in the month combined for a 24.0 mpg (9.79 L/100 km) rating, marking a 0.5% drop from March’s all-time high of 24.1 mpg (9.74 L/100 km).

The April rating represented a 14.6% increase in fuel efficiency over the index’s base rating of 20.9 mpg (11.2 L/100 km) established in fourth-quarter 2007. It also reflects a continuing trend within the market toward smaller, fuel-efficient vehicles.

Midsize Car was the best-selling segment for the third consecutive month in April, displacing Cross/ Utility Vehicle, which had led all segments for the 28 months prior to February.

Midsize Car accounted for 23.4% of all LV deliveries in April and, buoyed by increased sales of the Toyota Camry, averaged 27.3 mpg (8.6 L/100 km), the segment’s best index rating to date.

CUVs grabbed 22.4% of sales in the month, with an index rating of 22.2 mpg (10.6 L/100 km), the segment’s third best WardsAuto FEI showing.

Small Car deliveries slipped to a 19.9% market share from 20.9% in March, while attaining a second best-ever segment rating of 29.6 mpg (7.9 L/100 km), off a fraction from March’s record 29.7 mpg rating.

Pickup Truck, the index’s lowest-ranking segment with a fuel-economy of 16.9 mpg (14 L/100 km), earned its third weakest share since at least 1980, accounting for just 12% of U.S. LV sales.

While the overall slippage on the index was nearly imperceptible, Light Truck gained a full share point from March to account for 47.6% of LV sales in April. As a type, light trucks averaged 20 mpg (12 L/100 km) on the index, compared with cars at 27.2 mpg (8.6 L/100 km).

Vehicles averaging 20 mpg (11.8 L/100 km) or more accounted for 73.2% of the market, up 47% over the base period.

Those that earned an index rating of at least 30 mpg (7.8 L/100 km accounted for 11.1% of all LV sales, up 394% over the base period when vehicles rated at 30-plus mpg (7.8 L/100 km) accounted for just 2.8%.

Light vehicles with less than 15 mpg (15.6 L/100 km) fuel efficiency accounted for 0.7% of April deliveries, compared to 8.3% in the base period and 2.8% as recently as April 2011.

General Motors, which earned its lowest share of 16.5% in March since the first half of the 20th century, garnered 18.1% in April, while posting a 21.5 mpg (11 L/100 km) index rating for the month.

Toyota set a new record for all auto makers with 28.5 mpg (8.2 L/100 km) in April. The auto maker also earned its highest share in 16 months, accounting for 15.1% of LV sales and bumping Ford to No.3 for the first time since July 2010.

Hyundai, Kia and Volkswagen, finished in a dead heat for the No. 2 spot on the index, registering pretty much identical scores of 26.9 mpg (8.7 L/100 km) for the month.

Honda followed with a 25.8 mpg (9.1 L/100 km) index score, while also registering its highest share for the year of 10.3%.

Domestic-built LVs fell on the index in April to a combined 22.9 mpg (10 L/100 km) from an all-time high of 23.1 mpg (10.2 L/100 km), losing ground to imported cars and trucks that collectively rated 27.6 mpg (8.5 L/100 km), breaking the group’s previous high set in March.

The WardsAuto Fuel Economy Index rating for the U.S. industry in April remained at 23.9 mpg (9.8 L/100 km), retaining a 4.4% lead over like-2011.

jsousanis@wardsauto.com