I would have expected a better mpg. I tow my trailer (same as yours 2012 model) with a 2007 Toyota Tundra 4X4 and on the last trip I got b/t 11 and 12 mpg. I use the A/C and cruise control and keep it in the tow/haul mode. We went from 13' altitude to 7,200' and back. Around 45,000 miles on the Tundra so far. I use 87 octane (regular fuel).
Oh well, I love both the tow vehicle and the trailer. I bet you do too!
2012 Rockwood Windjammer 3008 W
2007 Tundra Reg Cab 4X4 SR5 5.7L