Two Sedans with some similarities, but otherwise different in most aspects such as the powertrain, modifications, horsepower, fuel economy, and ground shadow size. First of all, the 2015 Mercedes-Benz C-Class Sedan AMG C 63 has bigger and thirstier engine; the 2016 Audi A6 Diesel gets 10 more mpg. Also, the 2016 A6 Diesel has a slightly larger body than the 2015 C-Class Sedan AMG C 63. Among similarities are the body structure, market segment, starting price, height, and maximum occupancy.