Just got back from a 1,200mile trip in the 4.6L V8 Tundra, NH to DC. Family+popup camper, small one, guessing around 2,000lb of people+trailer+stuff, at most above and beyond the 5,400lb curb weight of the truck (so maybe GCWR of 7,500lb). Got about 18mpg going down as I needed to make time (65mph average I'd say), almost 20 coming back as I drove for mpg (stuck to 60mph on highway and 50 off)--and a pathetic sub-16 in some suburban driving (sans trailer) going from campground to the Metro. 18.5mpg overall. Last couple of tanks prior to our trip had been 20.7mpg.
The Jetta hit 53mpg on the last couple of tanks. The last tank yielded 900.1miles, it had to have been on fumes when I pulled in.