2001 Komfort 5 wheel
My Terry is rated at about 7200, dry weight is about 5200, I was towing it with water tank 1/3 full, so I would guess the weight to be in the 6000-6500 pound range. My truck (extended cab, long bed, 410 gears, towing package) gets about 12 MPG unloaded, around town. Pulling cross country (AZ to NY and back), I did not have any problems as long as the highway was level or downhill, cruise kept it right at the speed limit (usually 70 MPH). However, any up grade, the transmission would downshift, and usually the speed would drop down 5 to 10 MPH. I didn't go up any really steep grades (the worst was going west between Abilene and Albuquerque). At times during this stretch, I was limping along at 50 MPH and could not get it to go any faster. Neither transmission temperature or engine temp ever raised above normal. At low speed (20 MPH or so) I had no trouble up a short steep hill. I did not use the Tow/Haul mode, as the manual states that this is for when you are towing close to the truck limit and I was only at about 50%.
I haven't figured out the gas mileage exactly yet, but one relatively level stretch computed out to exactly 8.7 MPG, and an estimate between Abilene and Albuquerque was 6 MPG; possible, but suspect because the leg before that estimated out to 12 MPG.
The truck will probably do the job, just not always as quickly as one might prefer. I'm not looking forward to my first REAL up grade; I wonder if I would have been better off with the 8L engine...