The 2016 Mercedes-Benz SLK-Class is a 2-door, 2-seat Convertible, available in 2 trims, ranging from the SLK350 to the SLK300. Upon introduction, the $59,200 SLK350 is equipped with a standard 3.5L, 6-cylinder, engine that achieves 21-mpg in the city and 29-mpg on the highway. an Automatic transmission is standard. The $47,000 SLK300 is equipped with a standard 2.0L, 4-cylinder, engine that achieves 25-mpg in the city and 32-mpg on the highway. an Automatic transmission is standard.