Mileage is _very_ sensative to your speed and driving habits. I get 16 in the city. If I drive 65 mileage is 20 mpg. If I drive 80 mph it drops to 18 mpg. Improper tire pressure can drop your mileage as much as 10%.

The MLs are towing machines! The handling is fantastic. Better than any 1/2 ton pickup I've used and it rivals a 3/4 ton in everything but total weight capacity. I just returned from a 750 mile trip towing about 7,000 lbs. I have over 10k towing miles pulling loads between 1 ton and 3.5 tons.

Up to 5000 lbs it does not feel like there is a material strain on the engine. Above that and you are having to use high throttle positions for long periods of time and floor it to maintain speed up hills. IMO 3.5 tons is around the upper limit for long highway mileage.

Be sure and change the transmission and transfer case fluids before you start towing and I would change them every 40k miles afterwards.

Note that the hitch receiver sits pretty low. You may need a hitch that raises the ball quite a bit.

If you don't have the OEM trailer wiring you'll need a generic relay box. The truck comes stock with the hookup wiring and power supply for the relay already in place but the plug is custom. You just need to tie into the existing wires and the system will work fine. You'll need to add the fuse for the power supply.

If you don't have a receiver there are aftermarket units available that are simple to install. The frame is already pre-drilled to accept them. An OEM unit is very rare and gnerally very expensive.