All four wheels are powering the next step in the evolution of the luxury-car business: the rise of all-wheel drive.

The epitome of a high-performance, luxury sedan for many consumers has long been a car with a big six- or eight-cylinder engine driving the rear wheels. Now, cars that send power to all four wheels are gaining traction, accounting for half or more of luxury-car sales in the colder parts of the U.S. and as much as 15% of sales even in snow-free states, up from single-digit shares in the past. Many industry executives say all-wheel drive is now a must-have technology for the U.S. market.

'It's not even a debate,' says Jim Vurpillat, global marketing director for General Motors Co.'s Cadillac brand. Luxury-car buyers expect all-wheel drive to be available on any serious luxury sedan, he says, which is why Cadillac is offering the technology on its new compact ATS and large XTS sedans, as well as its midsize CTS model.

What is debatable is whether all-wheel drive delivers enough safety and performance benefits for the $2,000 to $3,000 extra charge car makers typically add to the price tag, as well as the mileage penalty that the extra weight of all-wheel-drive hardware still exacts in most cars.

The Highway Loss Data Institute compiled collisionstatistics for 10 popular midsize luxury sedans from the 2008-2010 model years that had both two-wheel and all-wheel-drive models. The all-wheel-drive cars had higher collision rates in four model lines, and lower collision rates for six.

Safety experts stress that all-wheel drive can help with acceleration on a slick surface, but it doesn't repeal the laws of physics governing friction, or the lack of it on snowy roads.

Consumer Reports compared the slick weather performance of a Toyota Corolla to a Land Rover and concluded that the Corolla -- with its thin tires and light body -- stopped much more quickly in snow than the burly, all-wheel-drive, luxury SUV, says Jake Fisher, Consumer Reports' co-director of auto testing.

Even industry executives who are pushing all-wheel drive into more models say demand for it is driven as much by emotion as hard data.

'It's about confidence,' says David Pryor, vice president of marketing for Jaguar Cars North American sales arm. Jaguar will offer all-wheel drive on its cars for the first time on its 2013 XJ and XF sedans. In the segment in which the $53,000 XF competes, Mr. Pryor says all-wheel-drive cars have moved in five years from just 30% of the market to about 50%. 'We haven't seen it plateau,' he says.

To boost the appeal of all-wheel drive, car makers and their drivetrain-technology suppliers are working to minimize the disadvantages, particularly in fuel economy.

Volkswagen AG's Audi luxury brand, which began offering cars equipped with its 'Quattro' all-wheel-drive system more than 30 years ago, is launching a new system that is lighter, and designed to improve handling and speed. The newly designed system that sends engine power to the wheels -- called a center differential -- weighs 11 pounds, down from 15 pounds in the previousgeneration system, says Barry Hoch, a product-planning manager for Audi's U.S. operations. The new system takes up less room in the car's chassis and is less of a drag on fuel efficiency.