I too experanced high oil temps while towing my TT in the mountains. I use Amsoil and was still a little worried at the oil temp spike and not coming down. I went a little different route and got a big cooler with a fan. It keeps the temp of the oil at 180 on very hot days. I have not towed yet but have a camping trip planned about 3 hours away at the end of the month.
Hear is the one I installed.