Nearly 17 feet in length, the A8 L is longer than the Mercedes S-Class and long-wheelbase BMW 7 Series models. Its wheelbase stretches 121.1 inches (116 inches on the standard A8), essentially identical to its European competitors and substantially longer than that of the Cadillac DeVille. Other things equal, a longer wheelbase offers more passenger room and increased stability at speed. The Audi is slightly wider than the Mercedes and comparable to the BMW. Its rear doors are long, allowing easy access to the rear seat.

All the doors open extra wide, making it easier to get in and out. The flush, lever-style outside handles are attractive, but we find them harder to use than the type you can put your hand through, such as those on a Mercedes.

The A8 4.2s feature seven-spoke 17-inch alloy wheels with 255/55R17 tires; these provide excellent handling and ride comfort and superb grip in the wet. The optional 18- and 19-inch wheels and tires more aggressively fill the wheel wells and provide a surprisingly smooth ride in spite of their short sidewalls. The 12-cylinder A8 L 6.0 gets the 19-inch wheel/tire package standard (20-inch wheels are optional).

The 6.0 features a tall, vertical grille the company calls "the new formal idiom of Audi design." The new grille connects Audi's familiar horizontally split grilles over the front bumper, emphasized with a chrome surround and chrome horizontal slats. It's similar in design to the grille on the all-new 2005 Audi A6. The 4.2 models feature Audi's traditional split grille.

The A8 L is the first car with LED headlights. Its low beams consist of five light-emitting diodes developed jointly with a California-based company. Audi says these lights draw considerably less current than halogen or xenon bulbs to deliver an equal amount of light. Less current draw means that the alternator, which generates a car's electricity, doesn't have to work as hard, and therefore robs less power from the engine. The A8 L 6.0 is the first car with daytime running lights that have virtually no impact on fuel economy, and full low-beam operation requires far less alternator draw than conventional lights.

The rear of the A8 models feature taillights that fit flush with the clean rear design. Turn signals use LED technology and feature side repeater lamps to signal your intentions to drivers alongside. Dual exhaust pokes from below the beautifully integrated rear bumper.

Audi also says the A8's aluminum space frame (ASF) saves about 300 pounds compared to a conventional steel frame, allowing more features without overburdening the car with weight. Still, an A8 L 4.2 weighs more than a BMW 745Li and more than an all-wheel-drive Mercedes S430 4Matic, both of which have more conventional steel-intensive construction. But the ASF offers other advantages. It uses fewer parts with fewer joints for increased rigidity. Increased rigidity means less flex, and the A8 feels as if it's milled from a single block of bar-stock aluminum. That improves just about everything else in the car, from ride quality to handling to overall smoothness.