Audi downsizes Q7 SUV, adds diesel plug-in

The Audi Q7, one of the biggest, most imposing SUVs on the highway, is being downsized. And the result will be substantially better fuel economy.

For even more fuel economy, there will be a version with Audi's first plug-in diesel.

The new one cuts 1.6 inches from overall length and about half inch from wide compared to the one it replaces. But Audi is quick to point out that it will offer an extra three-quarters of an inch in space between the first- and second-row seats. There's another 1.6 inches of headroom. The new one, which will be formally revealed at the North American International Auto Show in Detroit next month, is also substantially lighter.

Having shed 716 pounds, the new Q7 will be the lightest luxury crossover SUV in its class, according to Audi. Even at that, it will still weigh 4,398 pounds in its diesel version, according to Audi.

The lighter weight, made possible by a new chassis and lighter materials in the body, will pay off in fuel savings. Audi expects the gas engine to reduce fuel consumption by as much as 28%. The diesel should see a reduction off up to 23%.

Q7 will be powered by a 3-liter diesel V-6 that produces 272 horsepower or a 3-liter gas V-6 engine good for 333 horsepower. The diesel is designed to accelerate from zero to 62 miles an hour in 6.3 seconds. The gas engine is slightly quicker: 6.1 seconds. The plug-in diesel version will be able to go almost 35 miles on electricity alone before the diesel engine takes over, and there will be an all-wheel drive offering for it as well.