I would guess that towing 13k down the highway at 65 mph takes about 140 hp. If an engine is designed to put out 300 hp at 1700 rpm and 400 hp at 2800 I’m thinking it is lightly loaded towing a 13k trailer. The best rpm to tow at for fuel economy is not mystical. If a transmission control module is loaded with a BSFC map it is very easy for it to “know” exactly and instantaneously where it is on the map at all times. The decision to shift or not should be very simple for a computer ..... “I’m at 600 Nm at 1270 rpm and after the shift I’ll be at 1700 rpm and 450 Nm. My BSFC is better after the shift hmmm I think I’ll shift.” We have only a seat of the pants feel for where our trucks are running in relation to their BSFC map ..... especially when we have never even seen a map for our engine.
