If your towing, SW 3 is the max with that load on a stock tranny. Your RPM's are too low. I've found around 1900 is the magic spot towing, 1700 empty. Use OD on the stock tranny only on the downhills. If you don't keep the rpm's up the engine doesn't pump enough exhaust to power the turbo to provide enough cool air to feed the engine to burn the fuel efficiently. As far as your towing mileage....anything over 11.5mpg is good when loaded as you are. A bumper hitch trailer is a gas sucking leach. With the Quad in the back airflow is disturbed even more. If it was a fifth toyhauler you'd get probably 1.5 to 2 more mpg. Your empty mileage is another thing...The big tires cost you some mileage but if you keep them inflated a little more in the front....65 to 70psi then you should be ok.

The stock TC sucks for towing when it is unlocked....IF you add a lock up switch then you will get much better mileage towing and your tranny temps will stay reasonably cool. Good Luck, KS

 

I also am disappointed in the mpg's I am getting, albeit I have an '07 w/5.9 and now only 3600 miles. Anyway I just got back home to south LA from St. Augustine, FL on vacation. I pulled my boat (650 miles each way) locked on 75 tow haul on and off. Made no difference. I avg'd about 10-11 mpg at best. My boat and trailer weigh about 4000lbs with 50 gal of gas. I sure hope it gets better once it is broken in.

 

I had the Smarty at #3 before I got my XZT installed and I jumped maybe 1.5 MPG from pre-Smarty (stock tires). When I added the XZT, still with Smarty #3, I got an additional 5 MPG! I am currently getting about 23.5 MPG on the highway if that gives any perspective.