160 is fairly cold for oil temp so need to run the lighter weight oil.

I run Royal Purple XPR 5W-30 in my dyno engine. We try to get the oil temp up to 200 degrees but it is almost impossible to do even with a big heater in the oil tank. My oil lines are insulated which helps but the oil still cools off really fast. My engine will hold 80 psi at speed but at idle it drops down to about 30 psi hot.