June marked the fourth consecutive month in which the WardsAuto Fuel Economy Index remained at a record level of 24.3 mpg (9.7 L/100 km).

The month’s FEI score represented a 2.2% gain over year-ago and is 15.9% above the index base-period rating established in fourth-quarter 2007.

Cars recorded a 28 mpg (8.4 L/100 km) FEI score, a 3.4% increase over year-ago, while accounting for 49.3% of deliveries.

It was the third consecutive month light trucks outsold cars, but the expected downward effect on industry fuel economy has been offset each time by mix shifts and rising FEI scores within segments of both vehicle types.

Small cars earned a segment-best 29.9 mpg (7.9 L/100 km) rating in June, up 0.6% from like-2012, while midsize cars (28 mpg [8.4 L/100 km]) showed a 4.7% improvement over year-ago.

The luxury-car segment also set a record in June, with a 24.7 mpg (9.5 L/100 km) rating, while large cars maintained their all-time-high 21 mpg (11.2 L/100 km) average set in May.

Light trucks hit a new peak, as well, posting a 20.3 mpg (11.6 L/100 km) index rating, 1.2% over year-ago. Their 50.7% share of LV sales represented an increase from 49.6% in like-2012.

The improvement came in spite of a negative pull on industry FEI caused by pickup trucks, the lowest-rated LV segment and the only one to see its FEI rating drop from year-ago. Pickup fuel-economy fell 0.5% to 16.8 mpg (14 L/100 km), while the segment increased its market share nearly a full point to 13.3%.

The downward movement was more than offset by increased sales of the highest-rated truck segment, cross/utility vehicles (22.3 mpg [10.5 L/100 km], up 1.3%, and a record 17.8 mpg (13.2 L/100 km) average for SUVs.

General Motors scored a company-best 22.3 mpg (10.5 L/100 km) on the FEI, 2.2% over year-ago, aided by a boost in sales of the Chevrolet Cruze (29.4 mpg [8 L/100 km]) and its diesel-powered variant (33 mpg [7.1 L/100 km]). The Cruze accounted for 12.4% of GM’s June sales, compared with just 7.6% in the prior year.

Volkswagen claimed the top spot on the index in June, registering a company- record 27.6 mpg (8.5 L/100 km), a result of its sales shift in favor of cars and away from light trucks.

The WardsAuto Fuel Economy Index through the first half of the year reached 24.3 mpg (9.7 L/100 km), up 1.2% from year-ago.