At the risk of starting another octane war... agreed with other posters here, when towing, do not try to save a few bucks on gas, these hemis absolutely need 91+ octane as you can see if you start data logging your ECU. When coasting around in town, it's less obvious, but feeding it 87/89 is like trying to put in a full day of work with milkshakes and celery sticks.
As for the tow haul mode, I've found in my towing that it doesn't always pick the right gear, for me. I'd much rather rev a little higher and feel that there is power left in the pedal without a downshift, than having it lug and knowing that another slight dip in the pedal will cause a downshift. If you have that feeling, that a slight dip in the pedal = downshift, then you're next door to lugging it; if you're going up a hill like that, just downshift it manually.
If you're maintaining freeway speeds (63 mph), I tow my trailer in 6th and rev about 2300 rpms. Transmission would sometimes upshift, but I don't let it, and gear limit to 6.
When going up a hill, right before the hill I'll force a downshift so that the truck is already making more power before it hits the hill, sometimes gaining a bit of speed in the process, giving me a buffer to climb up the hill. Transmission won't automatically downshift until it is already working harder than it should be and losing a bit of power.
