We towed our RP175 for about two and a half years with our 4.6 Tundra. It did a fantastic job over all of the passes and foothills of Washington State. Towing mpg with the RPod was between 10 and 15 mpg--usually 12 to 13. The 2010 to 2013 4.6 Tundras were a little higher rated for towing (8200 lbs for mine) than the newer ones. I dunno why. I'm now towing up to 5000 lbs. wet weight with our Kodiak. Towing the big climbs of Colorado, Utah, and Arizona was no problem for the 4.6 at this weight. I always lock out overdrive 6th and sometimes 5th while towing.
P/S I also towed with a Tacoma, and it did OK, but got a little worse towing mpg than the Tundra 4.6, and couldn't come close to the towing ability of the 4.6. I know that the 5.7 Tundra is a horse for pulling, but most people don't give the 4.6 enough credit, as long as you keep it at a reasonable pulling weight.