[rwhyde]

Well, you certainly have your work cut out for you, but any improvement will or should be noticeable. Being a heavy vehicle reducing friction and drag will make a big difference. I second pumping up the tire pressures that will offer the quickest/easiest thing to do. On your coasting, moving the shift lever into neutral should help some as Mercedes tend to use a lot of engine braking, ( I have several and service many others), far more than our previous Toyota Highlander or my Prius. Next, I would look for at an oil change to the differentials checking the factory specs and ensuring I had the lightest weight synthetic lubricant the met MB specs in those to lower friction. The engine in this vehicle is pretty efficient, but is burdened with carrying a heavy load. Trying to lighten throttle application on take-off will yield a lot of improvement. Look for ways to unload the engine, A/C, alternator and other electrical loads to further improve mileage. Your weather might not permit that.