Standard A8 and A8 L models come with a 4.2-liter, 40-valve V8 that now benefits from direct fuel injection and makes 350 hp and 325 pound-feet of torque. Named after its special engine, the W12 model has a 6.0-liter, 12-cylinder engine that makes 450 hp and 428 lb-ft of torque. The W12 actually consists of two narrow-angle, 15-degree V6 engines joined at the crankshaft, which makes it more compact than a conventional V12. Both engines are matched to a six-speed Tiptronic automatic transmission that drives all four wheels through Audi's quattro all-wheel-drive system. Either way, this is a quick luxury sedan. The 4.2 V8 version can hit 60 mph in 6.3 seconds and cover the quarter-mile in 14.2 seconds, while the W12 betters those stats by about a half second in each case.