These two Audi A8 models are two types of the same model with one major difference, the powertrain. First of all, the 2015 Audi A8 has a more powerful engine and gets 8.5 mpg less than the 2016 Audi A8 Diesel. Also, there is a $7,800 difference in the base MSRP. The 2016 A8 Diesel has a higher starting price than the 2015 A8. Among similarities are the body structure, market segment, ground shadow size, and height.