19 mpg without the trailer @ 70mph (speed limit here)
19 mpg with the trailer @ 70mph
17 mpg with 25' full travel trailer
18 mpg with 21' bass boat on tandem trailer
14mpg with 38' Fountain on triple axle trailer, which is right at the maximum tow capacity for my 3/4 ton truck (not @ 70mph, normally I top out at 60ish with the boat)
2000 Ford F-250 Diesel. I could probably flip my tiny trailer (weekender style) upside down and drag it down the road and still probably get the same mileage as it gets rolling down the road.