It sounds like they'd have you towing at about 50-55mph max.I pull a 12,000 pound 5th wheel camping trailer with my 04 Duramax/Allison. Have to watch my speed as I hardly know it's back there. During visit to a local RV dealership, I was told that the "powercurve" for my truck indicated that the optimum RPM for towing was 1800 RPM. I have never heard of a "powercurve" to serve as a guide for the optimum RPM for towing a trailer. Is there an RPM at which I should drive that yields the most efficient return in terms of fuel consumption and interstate speeds? On non mountainous interstates, at 2000 rpm in tow mode and overdrive, I am pulling my 12,000 pound rig at approximately 65 mph. Any guidance will be appreciated.
Which truthfully isn't a bad idea to be keeping your speed low while towing.
You probably would find the best efficiency at about 50-55mph, but do you really want to be going that slow.
This is a very technical question that I'm sure others on here could answer for you, but I can't help but wonder if going 10mpg slower while towing with a diesel is going to make much of a difference. At least a difference that justifies dropping your speed like that.