I have a 3/4 ton Chevy Duramax diesel, Arctic Fox 31W and weigh around 18.5K. I average10.3-10.9 depending on the wind but average is 10.6 at 67 MPH on Interstate. I have an Edge computer and set at 60 HP above the normal for an 06. i get from 15.4 to 17.8 without the trailer and I believe it depends on where you buy fuel as some burns faster.
We went out and bought a Prius because Va decided to give us discounts on tolls and tags. Now they want to penalize us because we don't use enough fuel. Now they are going to tax everyone .05 for every mile they drive.