How far can you tow prior to fill up?

I hear the Eco Boost V-6 gets good mileage driving down the road empty, But hook a big rectangular camper behind it and the mileage goes down in flames. It's two turbo chargers let it squeeze the horsepower out of that little 6 banger to move that boxy trailer through the air at 70 MPH. But it has to burn a whole lot of fuel to do it. I wonder what kind of engine life those things are going to have over the long haul if they are worked hard the way Danasdaddy2002 engine will be working when hooked to that trailer. Gasoline engines have always had to struggle when working them hard and all the ones that I have towed with 57 on up have gotten horrible gas mileage when towing a full size travel trailer.
The only thing I would suggest is keeping the speed down below 60 and never using the overdrive when pulling that trailer. Your engine will thank you.