When towing my 5er and boat, I am about 17000 pounds towed weight. I put it in drive and let the computer shift. Sometimes I use tow/haul, sometimes not. My main complaint about that mode is it automatically begins down shifting every time I go to coast. Sometimes I dont' want that.
I have an app (car minder) where I track the miles. gallons, MPG, and fuel price of each fill up. My computer reading is usually very accurate. My 03 would read up to 3 - 4 MPG optimistic. Not the case with my 2012.
On a lighter note, the two things many truck owners seem to exaggerate are their MPG and the speed at which they can pull the passes fully loaded.
