ML350 diesel was great,and towed a 5700lb UVW through Yellowstone and Glacier with no problems. Conventional "truck" towing advice doesn't really apply..the euro TDI SUVs have excellent torque, used for both uphill grades, and engine braking downhill. Main thing is to ignore the old "15%" on hitch rule, and ensure you have weight in the trailer distributed above the axle, not the tongue. We had trouble until we shifted weight to the rear and center, made for a much easier tow. The old 15% tongue rule is probably needed for trucks due to their loose, bouncy suspensions, and long overhangs. Also note that you don't ever want to go above 65mph, and 60 is probably safer.
