By: Chester Dawson

Aluminum may not be the new steel, according to a new study, as auto makers’ use of a single predominant lightweight material such as aluminum in vehicles like Ford Motor Co.’s F-150 pickup is giving way to a patchwork of materials replacing heavier sheet metal.

Long seen as a lighter but far more expensive alternative to steel for automotive manufacturers, aluminum has enjoyed a surge as engineers scramble to shave weight amid tighter emissions standards. A new study to be issued Monday by DuckerFrontier says the use of aluminum in vehicles is projected to grow 42% over the next decade, but at a slower pace than in previous forecasts.

The average vehicle sold today weighs nearly 4,000 pounds and is made of rubber, plastic, steel, aluminum, upholstery and other materials. Auto makers have worked to make every component—from body panels and engines to brackets and windshields—lighter, often by substituting materials that can add costs but improve miles per gallon.

Ford’s shift in 2014 from steel sheet metal to aluminum for the best-selling F-150’s body panels, which represent a meaty portion of a vehicle’s structure, was seen as a tipping point for aluminum because sales and production volumes of Ford’s truck are so high.

Designers, more recently, have decided to use a mix of materials including magnesium and carbon fiber to achieve weight savings, and steelmakers have rolled out stronger but thinner, lighter steels

At the same time, the Trump administration is considering softening fuel economy regulations, which could slow so-called light-weighting efforts as urgency fades. 

“You’ll probably never see anything again that’s as aluminum intensive,” Dick Shultz, co-author of the DuckerFrontier study, said in an interview. While Ford slimmed down its F-150 by 700 pounds via aluminum, it also added $1,000 in costs per vehicle, he said while predicting the next generation F-150 would likely use less aluminum in favor of other materials.