its two archrivals Mercedes-Benz and BMW, favoring either front-wheel drive or all-wheel drive. The majority of Audi's lineup in the United States features all-wheel drive standard on most of its expensive vehicles (only the entry-level trims of the A4 and A6 are available with front-wheel drive), in contrast to Mercedes-Benz and BMW whose lineup treats all-wheel drive as an option. BMW did not offer all-wheel drive on its V8-powered cars (as opposed to crossover SUVs) until the 2010 BMW 7 Series and 2011 BMW 5 Series, while the Audi A8 has had all-wheel drive available/standard since the 1990s. Regarding high-performance variants, Audi S and RS models have always had all-wheel drive, unlike their direct rivals from BMW M and Mercedes-AMG whose cars are rear-wheel drive only (although their performance crossover SUVs are all-wheel drive). Audi has recently applied the quattro badge to models such as the A3 and TT which do not use the Torsen-based system as in prior years with a mechanical center differential, but with the Haldex Traction electro-mechanical clutch AWD system. Engines Prior to the introduction of the Audi 80 and Audi 50 in 1972 and 1974, respectively, Audi had led the development of the EA111 and EA827 inline-four engine families. These new power units underpinned the water-cooled revival of parent company Volkswagen (in the Polo, Golf, Passat and Scirocco), whilst the many derivatives and descendants of these two basic engine designs have appeared in every generation of VW Group vehicles right up to the present day. In the 1980s, Audi, along with Volvo, was the champion of the inline-five cylinder, 2.1/2.2 L engine as a longer-lasting alternative to more traditional six-cylinder engines. This engine was used not only in production cars but also in their race cars. The 2.1 L inline five-cylinder engine was used as a base for the rally cars in the 1980s, providing well over after modification. Before 1990, there were engines produced with a displacement between 2.0 L and 2.3 L. This range of engine capacity allowed for both fuel economy and power. 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°,