Improving share for fuel-economy leader Toyota and better index ratings for the Detroit Three helped lift the average mileage rating of light vehicles sold in the U.S. to a new high in January.

The average fuel economy of LVs sold in last month rose to 24 mpg (9.8 L/100 km), a 2.4% increase over year-ago and a 14.9% gain on the index base rating set in fourth-quarter 2007.

That bests the prior record set in March 2012 by a few hundredths of a rating point.

Mitsubishi led all auto makers with a record 29.2 mpg (8.1 L/100 km) index rating. The best-ever single-company score came as Mitsubishi phases out the less efficient Eclipse and Galant cars and Endeavor cross/utility vehicle, while boosting sales of its “i” electric car that boasts an Environmental Protection Agency fuel-economy rating of 112 mpg-e (2.1 L/100 km).

Mitsubishi’s 4,659 deliveries, however, had little impact on the overall industry mileage rating.

Toyota, the fuel-economy leader among high-volume auto makers, finished in the No.2 spot for January at 27.4 mpg (8.6 L/100 km) but grabbed 15.2% of overall industry LV sales – its highest market share in eight months.

Volkswagen finished third on the index with a company-best 27.1 mpg (8.7 L/100 km), reflecting a shift in its sales mix away from light trucks, as well as the recent addition of the Jetta Hybrid rated at 45 mpg (5.2 L/100 km).

Mazda’s 26.1 mpg (9 L/100 km) and Subaru’s 23.1 mpg (10.2 L/100 km) also set company benchmarks in January.

The Detroit Three, accounting for 45.7% of LV sales, combined for 22.1 mpg (10.7 L/100 km) rating, marking a 4.8% improvement over year-ago and the first time the group’s collective score broke the 22 mpg (10.7 L/100 km) threshold.

Chrysler boosted its rating 5.6% to a company best 20.5 mpg (11.5 L/100 km), with solid car sales adding balance to the auto maker’s sales mix.

Strong Fusion demand, growing hybrid deliveries and better light-duty truck fuel-economy contributed to Ford’s 8.2% year-over-year improvement to 23.7 mpg (9.9 L/100 km).

General Motors paired its 18.7% market share with a 21.7 mpg (10.8 L/100 km) index rating, a 1.3% gain from year-ago.

Small cars accounted for 19.4% of LV sales, while achieving a single-segment record 29.8 mpg (7.9 L/100 km) FEI rating, a 2.3% gain over year-ago. The midsize car rating rose 4.6%, as the segment took a 21.6% share of the market, while CUVs accounted for 25.2% of all LV sales with an FEI rating of 22.2 mpg (10.6 L/100 km), up 0.7%.

While the WardsAuto Small Car, Middle Car and Cross Utility segments individually have achieved higher market shares in the past, the three combined for 66.3% of January sales to set a post-Cash-for-Clunkers record, reflecting the collective popularity of the most efficient cars and light trucks.

Cars accounted for 50.2% of sales, nearly even with year-ago, while the vehicle type’s 27.6 mpg (8.5 L/100 km) FEI rating showed a 3.3% improvement. Light trucks, aided by higher efficiency ratings for Vans and SUVs and a continuing mix shift toward CUVs, scored a record 20.1 mpg (11.7 L/100 km) score, up 1% from year-ago.

jsousanis@wardsauto.com