I would say it depends on the actual truck set-up. But, I would expect mid to high teens if you drive it in the sweet spot. Most guys claim over 20 mpg, but I have only had a couple of tanks over 20 in the 6 years I've had mine. My truck is 4x4 and is a couple inches taller than stock, and I almost never drive it any real distance without a load.
Travis..