Currently in their fourth generation, Super Duty trucks use a separate chassis from the F-150, including heavier-duty frame, heavier steering and chassis components, which allows for heavier payloads and towing capabilities. With a GVWR over 8,500 lb (3,900 kg), Super Duty pickups are Class 2 and 3 trucks; chassis cab trucks are offered in Class 4 and 5 sizes. The model line also offers Ford PowerStroke V8 diesel engines as an option.