Making Vehicles Larger to Ease Fuel Economy Targets

Cars and trucks in the U.S. are getting larger, but it’s not just to give passengers more room. A larger footprint also nudges new models into less demanding fuel economy brackets, Automotive News notes.

That’s because current fuel economy standards are based not on weight but on the area defined by a vehicle’s wheelbase and track. Adding to the distance between the front and rear axles and making a car just an inch wider can lower its required fuel economy target by as much as 2 miles per gallon.

AN cites the remodeled Buick LaCrosse sedan as an example. The previous model’s corporate average fuel economy target was 37.7 mpg. The new version—whose track is 1.2 inches wider and which adds 2.7 more inches between the front and rear wheels— faces a CAFE target of 36.3 mpg.

AN says its analysis of 25 models that were redesigned before the new CAFE standards took effect in 2012, shows that 21 gained a larger footprint.

Regulators are aware of the math and say they are monitoring the industry trend. They also point out that larger vehicles can weigh more, which could offset the advantage of a smaller CAFE target. Engineers say carmakers also have been switching to lighter materials, which may offset the difference. In the case of the LaCrosse, the larger new model weighs 300 lbs less than its smaller predecessor.