The 2012 Mercedes-Benz SL-Class is available as a 2-door, 2-seat convertible. Starting at $103,650, the 2012 Mercedes-Benz SL-Class SL 550 is powered by a 5.5L , 8 -cylinder engine mated to an automatic transmission that returns an EPA estimated 14-mpg in the city and 22-mpg on the highway. The top of the line 2012Mercedes-BenzSL-ClassSL 63 AMG , priced at $ 140,440 , is powered by a 6.2L , 8 - cylinder engine mated to an automatic transmission that returns an EPA estimated 12-mpg in the city and 19-mpg on the highway.