GM won't follow aluminum strategy in future cars

General Motors Co. won't follow rival Ford Motor Co. in betting on aluminum vehicles, but instead will use a mix of aluminum, high-strength steel, magnesium and carbon fiber to cut the weight of future models, including its luxury sedans and pickup trucks, the auto maker's product development chief says.

Mark Reuss laid out new details of how GM plans to slash weight from its vehicles and meet tougher fuel economy rules in a lengthy presentation to analysts and investors at GM's vehicle proving grounds. For months, GM has ducked questions about how it will respond to Ford's decision to boost the fuel efficiency of its future F-series pickups by constructing the bodies out of lightweight aluminum.

Mr. Reuss, in a presentation somewhat overshadowed by the company's announcement of new financial goals, took an indirect jab at his Dearborn, Mich., rival, and other rivals that have highlighted strategies focused on building vehicles mainly from one lightweight material, such as BMW AG 's carbon fiber i3 and i8 cars.

"Frankly, making big statements around all carbon fiber, all aluminum, all magnesium, they're very interesting," Mr. Reuss said. But GM intends to use a mix of materials, he said, taking advantage of proprietary technology the company has developed to weld aluminum body parts together. GM is already taking steps to mix various lightweight materials on vehicles, and plans to expand that approach "rather than taking one product and changing over all of our plants and rolling the dice," Mr. Reuss said.

Cadillac's forthcoming CT6 sedan will have a body made of aluminum, high strength steel and other materials, and will be 100 kilograms (220 pounds) lighter than a similar-sized car made of high-strength steel, Mr. Reuss said.

Mr. Reuss said the lightweight-materials approach used for the CT6 "is manifesting itself in this whole portfolio" of future GM vehicles. "We know that the next generation of our trucks will have the basis of what we've talked about…baked into it."

Mr. Reuss also offered a snapshot of the future engine and electrification strategy for the Cadillac. The CT6 line will offer a six-cylinder, turbo charged engine capable of delivering about 400 horsepower, Mr. Reuss said. A version of the car will offer a new plug-in hybrid system he said would achieve the equivalent of 70 miles a gallon.