Vehicle Overview
Audi's S performance designation graces the automaker's largest sedan, the A8 flagship, in the form of the S8. The S8 is essentially the quickest A8 money can buy, and changes are few for 2008. Competitors include the Jaguar XJR and Mercedes-Benz S63 AMG.

It's hard to imagine a full-size luxury sedan moving quickly, but that's what the S8 does. Thanks to a 450-horsepower V-10, Audi claims it will scoot from zero to 60 mph in 4.9 seconds. The same engine powers Audi's S6, where it produces 435 hp.

For 2008, the S8 receives newly styled 20-inch wheels and new fog lights.

Distinguishing features for the S8 include its 20-inch split-spoke alloy wheels, subtle deck lid spoiler and a deep grille with prominent lower side portals. Low-profile P265/35ZR20 performance tires are standard, and aluminum door sills wear an S8 badge. The adaptive air suspension is sport tuned.

Thanks to the S8 sedan's 115.9-inch wheelbase, interior dimensions are plentiful. In the S8, sport seats are available in dual-tone leather upholstery. Power adjustment is standard. The steering wheel has three spokes instead of four, and it's trimmed in matching leather. Carbon fiber trim is optional.

The windows are double-glazed for better insulation, and the armrests are upholstered in leather. An optional 1,000-plus-watt sound system by Danish audio company Bang & Olufsen includes 14 speakers.

Under the Hood
A 5.2-liter V-10 utilizes Audi's direct fuel injection technology to produce 450 hp and 398 pounds-feet of torque. It's mated to a six-speed automatic transmission with Tiptronic manual shifting. In the S8, Tiptronic has been modified to allow for higher shift points and faster response. All told, the S8 accelerates a hair faster than even the 12-cylinder A8 W12, which costs substantially more.

Quattro all-wheel drive is standard.

Ten standard airbags include dual front airbags, front knee airbags, side curtain airbags and front and rear seat-mounted side-impact airbags. Four-wheel-disc antilock brakes and an electronic stability system are also standard.