being compulsive about engine oiling, and minimzing flow resistance, i re-did my SPF's external oiling with a full AN 12 system, including new
oil cooler. I run a big Ex NASCAR filter mount, off of one of the Evernham Dodges. Huge Wix racing filter.
I have rigged up a winter and a summer oiling system, so i by-pass my
oil cooler until the weather temps warm up, then in about ten minutes i can switch one AN 12 line, and hook up the cooler. If it is cool out, i have a nice aluminum cover i have i pop on the cooler.
I think this is much less complex and allows the shortest hose length, and offers less resistance to
oil flow, than adding an oil thermostat to the system.
I have also found that moving the oil temp sensor from the filter mount to the Aviad pan gives a very different oil temp. My oil temps are much cooler in the sump than at the artificially elevated temps in the oil filter, due to the heat added to the relatively small amount of oil (by the oil pump) at any one time going out of the engine.
My engine oil temps, unless i am hot-footing it, or idling in traffic, rarely get up to a sufficent temp even with my cooler totally out of the system. I think my pan radiates a lot of oil heat, so it actually hinders my oil coming up to temp, even without the additional cooling of the front cooler. So just going out and back to the filter doesn't let my oil get warm enough. I have tested my oil temp gage, it is accurate.
So by and large, a thermostat would not make much differerence, except for shortening the warm up time. My engine runs at 180 degrees.
I also suggest that you not rely on your temp sensor to be an accurate temp of your sump's temp, if you have the sensor in the filter mount. Big difference in my engine.