Despite the fact that BMW and Mercedes-Benz have enjoyed a considerable head start in the field of large luxury sedans, the Audi A8 has proven it's a fast learner. When it comes to feature content, performance and prestige, the A8 holds its own against long-refined rivals like the BMW 7 Series, Mercedes-Benz S-Class and Lexus LS. The 2014 Audi A8 receives a number of enhancements to keep pace with its posh competition, including a new diesel-powered TDI model that returns best-in-class fuel economy. Buyers may also choose between a standard wheelbase and long-wheelbase "L" versions, with the latter boasting an additional five inches of legroom. As for blending the highest levels of luxury and performance, you'd be hard pressed to do better than the 520-horsepower Audi S8.