U.S. March light-vehicle sales earned an overall 22.4 mpg (10.5 L/100 km) rating on Ward’s Fuel Economy Index on the same day the U.S. government announced new tougher federal fuel efficiency goals, which will culminate in a mandated fleet average fuel economy of 35.5 mpg (6.6L/100 km) for 2016 models.

The results put the challenge facing automakers in perspective: Of the 1,063,872 light vehicles sold in March, only 16,482 (1.6%) had an index rating of 35.5 mpg or better.

March fuel economy rose 0.3% from February and gained 0.5% on year-ago, bringing the industry’s year-to-date rating on the Ward’s FEI to 22.4 mpg, up 1.2% from like-2009.

The relatively flat month-to-month efficiency rating came as fuel-economy leader Toyota Motor Corp. lifted its market share from 12.8% in February to 17.6%, but saw its FEI rating fall from 25.3 to 24.9.

Ford Motor Co. scored a 20.7 on the index, its highest rating not associated with the “Cash-for-Clunkers” program, but saw its market share fall from 18.1% to 17.1%.

Related document: Ward’s Fuel Economy Index

General Motors Co., which regained large-pickup market share lost in February, experienced the biggest month-to-month downturn in fuel economy in March, with a fleet average of 20.6 mpg (11.4 L/100 km), down 2% from the prior month but 2.2% higher than year-ago.

Hyundai Motor Co. Ltd. held the No.2 spot on the index with a 24.4 rating, down 1.1% from February, while America Honda Motor Co. Ltd. fell 0.5% to finish third with a 24 rating.

The biggest gainer on Ward’s the FEI was Porsche AG, which saw car sales rise 49.4% while deliveries of its Cayenne cross/utility vehicle fell 38.8%, boosting the auto maker’s rating 6.2% to 19.8 mpg, its highest score to date.

Domestically built vehicles, which include the majority of large trucks, finished with a 21.7 rating, up slightly from February. Import vehicles lost some ground, scoring 24.4. The resultant 2.7 point difference was the narrowest since February 2009.

Ward’s Fuel Economy Index was recalibrated in March to reflect updated engine-survey results and history was restated accordingly.

jsousanis@wardsauto.com