The Mercedes-Benz GLS63S V8 is an all-new model, to compete against the BMW X6. Mercedes-Benz GLS 63S V8 is the top performance model. Under the hood, both come with the 5.5 literturbocharged V8 engine, mated to a 7-speed automatic transmission and all-wheel drive. Available features include adjustable air suspension, adaptive cruise control and active parking assist.