The 2009 Mercedes-Benz CLK-Class is a 2-door, 4-seat Convertible, available in 4 trims, ranging from the CLK350 Convertible to the CLK550 Coupe. Upon introduction, the $56,100 CLK350 Convertible is equipped with a standard 3.5L, 6-cylinder, engine that achieves 17-mpg in the city and 25-mpg on the highway. an Automatic transmission is standard. The $56,800 CLK550 Coupe is equipped with a standard 5.5L, 8-cylinder, engine that achieves 15-mpg in the city and 22-mpg on the highway. an Automatic transmission is standard.