Pretty sure I read somewhere that the stock oil thermostat opens at 230F/110C, fully open at 260F. That's pretty high. For a DD it doesn't really too much but for highly modded cars and/or people that track them it opens about 20-30 degrees to late. That's why I bought the Mosselman thermostat since it starts to open at 185F and says it'll stabilize between 200-220F. Which is perfect - I'm expecting it to hover around 200-210F with my planned dual oil coolers.
I can see a problem with 200F oil as moist isn't burned off over time?
I don't see the problem with 230-260F oil. This is oil temp measured in the oil sump remember. I mean sure, a thermostat that fully opens from 220F-230F would be better, but why 185F?
I do see a problem with coolant exceeding 212F when the DME is trying to target 176F though... This is again why I suggest focusing on adding aux radiators rather than oil stuff.
Here's a log from last weekend. Did a 20min session on a semi-wet track in 85F humid heat. I was a bit annoyed coolant got so hot (223F) considering I was barely pushing. The DME was clearly trying to target 176F, as was finally achieved at the end of the cool down lap. Oil temps on the other hand were low enough (max 270F or so) that I didn't even care to turn on the second oil cooler on my car. WI and external water spray was both turned off. AC was also on, which never helps coolant. As most of you know I run two large aux radiators, one on the side, one behind fmic.