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General Motors Vehicles Shed Weight to Boost Fuel Economy

General Motors has put its vehicles on diets. Seven of its newest models have lost a combined 2,400 pounds compared with the models they replace.

For consumers, lighter vehicles mean lower gas expenses, as these cars consume less fuel and emit less carbon dioxide. GM claims its seven newest vehicles will save a combined 15 million gallons of gas. Lighter vehicles can also provide more nimble handling, a quieter ride and enhanced safety.

But the real driver for lightweight vehicles is stricter fuel efficiency and emissions regulations globally. Meeting future rules will require automakers to produce lighter vehicles, improve engines, introduce advanced powertrains — electric, fuel cells and hybrids — and build in fuel-saving technologies such as start/stop, a feature that shuts off the engine as the vehicle idles at red lights. GM says it will have 30 models with stop/start by 2018.

Material World

While Ford gained attention for its mostly aluminum F-150 pickup, General Motors has adopted a different strategy by using an array of lightweight materials.

“No single metal is the right metal for every vehicle and every part,” said Charlie Klein, GM’s executive director of Global CO2 Strategy and Energy Center. Instead, GM engineers select materials based on the vehicle category and also consider price, performance requirements and consumer expectations.

The 2016 Chevrolet Malibu, starting at just under $22,000 in the competitive midsize-sedan category, uses a variety of steels instead of more costly metals like aluminum. The new Malibu weighs 300 pounds less than its predecessor, although its body is longer. Its fuel economy is rated at up to 27 miles per gallon in the city and 37 mpg on the highway, an increase of a mile per gallon in each category from the 2015 version.

Meanwhile, the 2016 Cadillac CT6, starting at just under $54,000, uses nearly a dozen different metals, including various types of steel and pricier aluminum. In the CT6, light weight is critical for performance, as the vehicle competes against German luxury-sport models.

Lightweight Lineup

Other new GM models that now feature lower weights include the Chevrolet Volt and Chevrolet Cruze, each of which are down 250 pounds. The Cadillac XT5 is down 280 pounds from the SRX it replaces, while the 2017 Buick LaCrosse has shed 300 pounds. And the new GMC Acadia weighs 700 pounds less thanks to a considerable downsizing.

GM is also researching other materials: Magnesium, for example, could cut wheel weight by half compared with aluminum and reduce the heft of door frames. And the brand is exploring additional uses for pricey but lightweight carbon fiber.

The automaker’s efforts also include investigating new methods of forming and joining metals. Their team is developing adhesives and innovative welding techniques to replace metal rivets, which add weight. Processes for bonding metals with different properties — aluminum and steel, for example — are also in the works. GM engineers say weight could be halved if an aluminum roof could be bonded to a steel frame. They’re also redesigning certain components to shed weight, such as swapping out straight edges for scalloped ones on some metal parts.

According to Klein, all of these efforts play a role in GM’s new company mantra: Every gram matters.

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