My '09 w/ the variable valve timing Hemi gets 10.5 to 12 in town, up to 15 highway if I don't exceed 2200 RPM. With 35's that translates to about 68 MPH on the road, well below the speed limit. At 75 MPH or above it drops back to 10 to 11.
Off highway when aired down to 18 PSI, mileage drops to 8 or 10 MPG. Snow, sand, or mud requiring lower pressure or just pushing thru drops it further to around 6 to 7.
Towing a 3500 lb StarCraft RT10 on the highway didn't hurt it much - it was about 11. Once I aired down, it did what it usually does - 8 to 10. I haven't towed over 6K with mine, so I have no data on heavier towing.