We just finished a 10 day camping trip up to Lake Vallecito near Durango, CO. If you ever get a chance to make it that way check out the Blue Spruce RV Campground. It's one of the best run and nicest campgrounds you can find!
I'm guessing my Toy Hauler packed (w/o a toy) is somewhere around 6800 pounds. We had about 10-15 gallons of fresh water, 10-15 gallons of fuel in the fuel station, and of course all of our camping gear.
The trip is about 850 miles and we broke it up into 2-3 hours stops. It never fails that I seem to hit a huge crosswind or head wind when towing. This trip was no different and yielded the worst gas mileage I've seen with the truck. Granted this is up hill most of the way. Speeds were between 55mph - 63mph.
First stop, 223 miles, 30 gallons @ 7.4MPG
Second stop, 128 miles, 15.5 gallons @ 8.2MPG
Third stop, 115 miles, 15.2 gallons @ 7.6MPG
Forth stop, 110 miles, 13.0 gallons @ 8.5MPG
Fifth stop, 214 miles, 23.4 gallons @ 9.1MPG