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Weight is a problem when it comes to fuel economy. The heavier something is, the more energy you burn moving it down the road. The engineers at Cadillac tackled this problem head-on with the new CT6. Rather than relying on expensive carbon fiber or heavy steel, they created a lightweight chassis from a new composite. The result marries 11 materials including high-strength steel and lightweight aluminum, shaving 198 pounds off the traditional chassis.

Available as a hybrid—making it the first full-size electric luxury sedan—the car’s drivetrain takes fuel efficiency a step further. An 18.4 kilowatt-hour lithium-ion battery powers an electric variable transmission capable of boosting acceleration without spasmodic jolts. As for the gas-powered half, it’s a small 2.0-liter four-cylinder engine. Combined, they provide the CT6 with a respectable 335 horsepower.

All this adds up to a luxury hybrid with more than double the mileage of its gas-powered counter­part. But true Caddy lovers will appreciate the new agility brought by the car’s electric engine. The CT6’s 2-ton rivals might want to invest in a treadmill.

This article was originally published in the August 2015 issue of Popular Science, under the title “Cadillac Introduces Lightweight Luxury.”