BG, the temp keeps at the 140 to 150 range while towing small grades. It will climb up to the 170 range going up steep grades towing the car hauler. Once it starts down the grade the temp will lower to the 140 range again. While not towing it will stay at the 140 range no matter what the outside temp gets. If I get into heavy freeway traffic the temp rises a little off the 140 range, but not enough to worry.