Mercedes estimates 0-to-60 mph in 4.5 seconds for the CL600, with its 510-horsepower/612-pound-foot 36-Valve 5.5-liter V-12 and 5.4 seconds for the CL500, which has the 382-horsepower/ 391-pound-foot 36-valve 5.5-liter V-8. As with other models, the V-8 is coupled with a seven-speed automatic; the V-12 has a five-speed autobox.