I have an
oil cooler, with no thermostatic valve on it. My
oil temp tends to track with coolant temp, generally around 185 degrees in the summer, and it doesn't get driven in the winter. I recently posted a thread on my
oil analysis after having the car sit for four months and the oil having not been changed in four years. There wasn't a molecule of moisture that showed up and the oil temperature articles that aren't "shooting from the hip" peg the temperature for the least amount of engine wear at the low 180's. Here are two typical articles of that ilk:
The heat is on: Our experts agree on the best oil temperature and
Elephant Racing | Tech Topic | Oil Temperature and Engine Life and there are many others.