2006 BMW 325xi Sports Wagon

The latest xDrive system (available in the 325, 330, 525, and 530 sedans, and the only drivetrain available in 325xi and 530xi Sports Wagons) is designed for a low center of gravity and optimal dynamics with minimal intervention and "extremely fast response times," BMW engineers say. (xDrive won't be available on the 7 Series until the all-new 2009 model.) The latest-generation xDrive, an update over what's in the X3 and X5 (there's no space for the SUV's transfer case in the cars), is integrated with the dynamic stability-control (DSC) system to provide a safety and handling benefit that'll satisfy most enthusiasts. The aluminum front axle is placed high up, through an opening in the oil pan, and the clutch can lock up completely when sensors detect the need for hard-core traction. Normal torque split is 40/60 front/rear, but the system can transfer all the torque to the front wheels. xDrive adds some 250 pounds.

How does it work? With good winter tires, like a rally champ on Arjeplog's ice circles and snow routes. You can mindlessly floor the throttle, and the DSC will work with xDrive to get you motivated efficiently, if not quickly. The DSC catches you if you turn in too fast. The hand of the Bavarian gods lets itself be known, although not as resolutely as an AWD Benz or Lexus.

Turn the DSC off, and you can play junior rally driver, sliding the car around an ice circle or drifting it on an icy road course, so long as you're prepared to pull it off a snow bank. xDrive is a worthwhile option on sedans if you're in schussing around in a far-northern climate, but enthusiasts facing more moderate weather will be happier with a set of winter tires and the lower weight and better balance of rear drive.