I should have also said: I tow in OD as long as the terrain is not too hilly. My RPMs are about 1800-1900, I believe. If it drops out of OD, the RPMs go up to 2300-2400, like yours.

I know what you mean about bugging Bill. He seems like such a busy guy it's hard to do it. However, he seems very open to being contacted and has never made me feel like I'm a bother.

- Jack

That sounds way low for gas mileage to me, glockwinger. I've averaged 12.9mpg over 2300 miles pulling the trailer through Colorado which included over two 11,000+ foot passes. I think the lowest value I saw at fillup in this trip was about 11mpg and the highest was around 14. My trailer is 3600#, but, it's a HiLo trailer, which means it is only 71" high while being towed, giving it fairly low wind resistance. It rises to normal height at the press of a button when you stop to camp, sort of like a tent trailer (except it has hard sides).

I wonder if you have the correct tire size set in? When I load the custom tow tune, I have to go into the custom menu and reset my tire size to 2481, which is what I've found makes the speedometer and odometer accurate. By default, if I didn't do this, the tire size would be 2356, which would cut the distance recorded (and the gas mileage by about 5%).

My truck has the factory tow package, 3.73 gears and 275/65R18 tires. Are you possibly geared higher or do you have taller tires? I pull the trailer at 65mph on the interstate, somewhat slower on country roads. Faster would eat gas.

I'd talk to Bill about this if you can't figure out a good reason. I'd think pulling even a high profile trailer, you'd get at least 10-11mpg.

- Jack