I usualy watch the Scangauge water temperature and with no A/C in the hills I pull of the throttle before the fan comes on full at about 116F. With automatic transmission it is all related as the water temperature goes up with the oil temperature. With fan not loaded I save up to 35 HP applied to pulling the load up the hill. It's a Mather of training, being able to make the long hills. Notice the speed of the transports, they have experience in the hills.
I will never be without my ScangaugeII digital readings while towing. Still wonder why a 70k $ truck has so many dummy gauges we can never read right.
Barbara and Laurent, Hartland Big Country 3500RL. 39 ft long and 15500 GVW.
2005 Ford F250 SD, XL F250 4x4, Long Box, 6.0L Diesel, 6 Speed Stick, Hypertech Max Energy for Fuel mileage of 21 MPusG empty, 12.6 MPusG pulling the BC. ScangaugeII for display..