The 2015 Mercedes-Benz SL-Class is available as a 2-door, 2-seat convertible. Starting at $106,900, the 2015 Mercedes-Benz SL-Class SL 550 is powered by a 4.7L , 8 -cylinder engine mated to an automatic transmission that returns an EPA estimated 17-mpg in the city and 24-mpg on the highway. The top of the line 2015Mercedes-BenzSL-ClassSL 400 , priced at $ 84,000 , 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 27-mpg on the highway.