I have a 2007 TCH with just a shade over 2,500 miles on it (I know, I dont drive it much. I have a 1997 Tacoma I use in my business and during winters here in Montana)
Last week on a trip from Kalispell MT. to Missoula MT. and back I used 6.3 gallons of fuel to travel 257.1 miles. This it up and down some pretty steep grades at legal highway speeds (mostly 75 miles per hour.)
Tires @ 36psi (Michelin MXV 4's)
Mobile 1 0W20 synthetic oil
Didn't use the cruise at all
I'm happy with that mileage, I usually get around 38 to 39 mpg around town.