I have e-rated tires, and now a boxy tent on my roof. I get 20+ mpg on the highway and 17 in the city... as long as I keep the speeds reasonable. When the speed limit says 55, I get 21mpg or higher by sticking to it. When I push it to 70, mpg drops to the mid teens. The first year we got it we drove to Yellowstone, we were getting mid-20 in the park because we stuck to the 45 mpg limit.
For you new TE owners, reset your mileage counter before you get on the highway and then see what it is at the end of your trip (long, short... doesn't matter) and then compare that with what your computer is reporting now. If you have the Nav, hit the Info button and check the fuel consumption screen as you are driving... it'll show you haw much of a leadfoot you really are.