A good friend of mine has the Tundra SR5 with the TRD 4x4 package 5.7 super charged and all 598hp and gets still around 18mpg unloaded and 14 pulling his 34 foot camper, he upgraded from his first Tundra because it didn't have enough power to pull the camper up hill or should I say at HWY speeds, and with the V6 he only got 7 MPG pulling the camper because he had to floor it so much.
But the price tag with all the options he had was steep, over $50k but it was decked out.
With the TRD package he got over sized suspension hydro boost braking Detroit style locking axles, much larger load range E tires, he let me drive it for work while my car was getting some recall repairs (2010 Corolla), and I couldn't believe how much power it had, I loved the way it handled he said he had the Allison trany option and you could feel it shift 7 times when it goes into over drive and when you use cruse control it engine brakes to maintain speed on down hills.
Now if Toyota would come out with a full sized work van with the options that this tundra had I would buy it in a heart beat, I drove a Nissan 3/4 ton HD van it got very bad millage and corner roll was bad, felt like I was driving a boat, guess I was used to my 2005 Express 3/4 ton with the anti roll system they used