For the ultra-luxury version of its Audi A8 fullsize luxury flagship sedan, the Audi A8L W12, Audi uses the Volkswagen Group W12 engine instead of the conventional V12 engine favored by rivals Mercedes-Benz and BMW. The W12 engine configuration (also known as a "WR12") is created by forming two imaginary narrow-angle 15° VR6 engines at an angle of 72°, and the narrow angle of each set of cylinders allows just two overhead camshafts to drive each pair of banks, so just four are needed in total. The advantage of the W12 engine is its compact packaging, allowing Audi to build a 12-cylinder sedan with all-wheel drive, whereas a conventional V12 engine could have only a rear-wheel drive configuration as it would have no space in the engine bay for a differential and other components required to power the front wheels. In fact, the 6.0 L W12 in the Audi A8L W12 is smaller in overall dimensions than the 4.2 L V8 that powers the Audi A8 4.2 variants. The 2011 Audi A8 debuted a revised 6.3-litre version of the W12 (WR12) engine with .