Shiner I really don't think we are that different in how we understand things. For one thing I am giving the Ram/Cummins engineers a bit more respect than you do. I believe with today's technology it is not that difficult for an engineer to program a transmission to select the right gear for the load being towed. The truck computer has a lot more information to base things on than you do. Based on what you have posted I would likely lock out 6th gear with your truck if I was towing 13k at 60 mph. If I was towing at 65 mph I would definitely be in 6th unless the terrain, wind or traffic conditions were such that the tranny was shifting back and forth. Between 60 and 65 I really doubt it would make much difference what I did.... According to the BSFC map that you posted the fuel economy would be the same.... Likely about 9.5 mpg.
