Two Sedans with more similarities, such as the body structure, market segment, starting price, and maximum occupancy, than differences, like the horsepower, fuel economy, ground shadow size, and height. First of all, although the 2016 Audi S8 has a more powerful engine than the 2015 BMW M6 Gran Coupe, it gets 2 more mpg. And finally, not only 2016 S8 is slightly larger, but it's also taller than the 2015 M6 Gran Coupe. Among similarities are the body structure, market segment, starting price, and maximum occupancy.