I turn my OD off, unless towing flat, straight, and level (interstate). Prefer to manually shift up or down in hilly country, as needed. Cruise control - I do not use when towing my 11,000 5er, , as it cannot anticipate hills, where I need to accelerate slightly to maintain speed. I down shift going both up and down hills - like a bicycle, it's easier on the engine with more revs going up, and uses the engine as brake going down. Just my way of doing things - hope this helps.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.