The 2016 Mercedes-Benz SL-Class is a 2-door, 2-seat Convertible, available in 2 trims, ranging from the SL550 to the SL400. Upon introduction, the $108,050 SL550 is equipped with a standard 4.7L, 8-cylinder, engine that achieves 16-mpg in the city and 24-mpg on the highway. an Automatic transmission is standard. The $85,050 SL400 is equipped with a standard 3.0L, 6-cylinder, engine that achieves 20-mpg in the city and 27-mpg on the highway. an Automatic transmission is standard.