The 2009 Mercedes-Benz SL-Class is available as a 2-door, 2-seat convertible. Starting at $98,500, the 2009 Mercedes-Benz SL-Class SL 550 Roadster is powered by a 5.5L , 8 -cylinder engine mated to an automatic transmission that returns an EPA estimated 13-mpg in the city and 21-mpg on the highway. The top of the line 2009Mercedes-BenzSL-ClassSL 65 AMG Black Series Coupe , priced at $ 299,000 , is powered by a 6.0L , 12 - cylinder engine mated to an automatic transmission that returns an EPA estimated 12-mpg in the city and 18-mpg on the highway.