I am concerned about mileage too as I drive conservable as to not waste fuel. 65mph-1800/1850 rpm seems to do best. I have never been able to get any reasonable idea of fuel mileage I actually get. We never go the same route with the same road conditions or weather. I try to fuel up at around half to quarter tank. Half makes it seem easier on the wallet. The best I have figured is 7.5 never been able to get 8 yet but have seen 6 a couple times. I think to get any accurate idea you would have to be in a controlled environment and that is not what we purchased this rig for anyway. It cost to move these things down the road. Larry