The A8 4.2 rides on a 115.9-inch wheelbase, while the A8 L adds 5.1 inches in both wheelbase and overall length. Both are powered by a 4.2-liter V8 rated at 350 horsepower and come with a six-speed automatic transmission with Tiptronic manual shift control. Both models come loaded with all the luxury features you'd expect at this price point. The air conditioning uses temperature, moisture, and infrared sensors to demist the windows before they can even think about fogging. The parking brake is operated by a switch.

The A8 L W12 rides on the 121-inch wheelbase and is powered by the 450-hp W12 engine. It comes with ultra-luxury amenities such as power sunshades for the rear windows; heated power-adjustable rear seats; and leather upholstery on the door panels, console and dashboard. The A8 L W12 also comes standard with a full-length rear-seat center console, housing elaborate climate controls and seat adjustments, plus a dual-screen entertainment system; this limits seating capacity to four, though the rear center console can be deleted at no cost in favor of a three-place bench seat.

The S8 rides on the standard 115.9-inch wheelbase, and features a high-performance 5.2-liter V10 rated at 450 hp. The air suspension is firmer, the brakes are larger and the steering is quicker. Extra bright trim and 20-inch wheels contribute to a distinctive look outside; while inside are sport seats upholstered in two-tone leather, darker wood or carbon fiber trim with aluminum accents, and white-on-gray italic gauge faces.

Option packages for the A8 and A8 L include a Sport Package ($2,800) with firmer suspension settings, 19-inch wheels with P255/40R19 summer performance or all-season tires, and a multi-function leather-wrapped three-spoke steering wheel with shift paddles. A similar package is available with 275/35ZR20 performance tires on 20-inch wheels ($4,000). A 14-speaker, 1000-watt Bang & Olufsen sound system custom-tailored to the Audi's interior acoustics ($6,300) is available. A Premium Package ($4,400) includes Advanced Key, heated front and rear seats, electric rear sunshade, manual side sunshades, power trunk open/close, power door-close assists, Advanced Parking System with rearview camera, and rear vanity mirrors.

Options for the A8 and A8L include adaptive cruise control ($2,100), which uses radar to maintain a prescribed distance from traffic ahead; Sirius Satellite Radio ($550); four-spoke wood and leather multifunction steering wheel ($690); a solar-powered sunroof panel ($790) that blows cooling air through the car while it is parked (and replaces the standard glass sunroof); front seat massage and ventilation ($1,500); rear-seat electric lumbar adjustment ($350); dual rear-seat climate control ($600); a ski sack ($175); 19-inch wheels with all-season tires ($1,900); and, for the A8 L only, personal refrigerator ($1,500) in the trunk accessible through the rear-seat armrest. Special paint-and-leather combinations are available ($11,500).

A8 L W12 options are limited to the adaptive cruise control, solar roof panel, four-spoke multi-function steering wheel ($200), Bang & Olufsen stereo, refrigerator, full-leather upgrade ($3,900), and 20-inch wheels ($3,200).

S8 offers the Premium Package ($3,900) with powered rear and manual side sunshades, Advanced Key, power opening and closing trunk, power assists to gently close the doors, heated rear seats, and Advance Park System with rear-view camera. Most of the stand-alone luxury options offered on the standard-wheelbase A8 are available on the S8 for the same prices. Carbon-fiber interior trim ($550) is available.

Safety features on all A8 models includes 10 air bags. In a crash, computers quickly determine which dual-threshold, dual-stage air bags to deploy, how quickly to deploy them, and how intensely they should be deployed. The A8 comes with excellent seat belts. Be sure all your passengers wear their seat belts because they are critical to providing protection in a crash.