The 2020 Mercedes-Benz SL 450 is available as a 2-door, 2-seat convertible. Starting at $91,000, the 2020 Mercedes-Benz SL 450 SL 450 is powered by a 3.0L , 6 - cylinder engine mated to an automatic transmission that returns an EPA estimated 20-mpg in the city and 28-mpg on the highway.