Do you have an oil pressure gauge installed? At 115 C, with 0w20 you oil pressure will be in the low 40s psi. Having both oil pressure and temp gauges installed, I would back off when I saw this. Oil temp/pressure is a function of rpm. Even having fun on a back road, it doesn't take long.
I read everything I could on here on oil, oil temp and oil pressure. I found out no one really knows what readings are bad for this engine. Low 40psi-probably bad. 132 C oil temp-probably bad. 0w20-depends on how your driving.
So, when having fun, if I saw oil temps at 118 C (just based on oil pressure), I backed off and let it cool down. This was frustrating. To help with this, I bought the oil/water cooler set-up (Cusco) installed it and set to driving. It does help the oil warm up faster. IT DOES NOTHING TO LOWER YOUR PEAK OIL TEMP. It does help the oil cool down faster. It may have taken a few psi off my oil pressures. Nice unit, now sitting in a box in my shed.
Then I bought a really nice Air to Oil cooler unit and installed. Wouldn't stop leaking. Yes I bought the proper wrenches, read about torquing flats, got flare savers. Wasn't leaking at the An fittings. No testing on this. It also is sitting in a box in my shed.
The I found this thread:
https://forums.nasioc.com/forums/sho....php?t=2714154
Lots of good info. there. The Stribeck curve, etc. Read it all. To summerize, oil temp matters in regard to viscosity, match your oil to your temp. Cst.
Now I run a 5w30 Castrol C3. Oil pressure stays in the low 50s psi at 118 C the max temp I have seen. I don't back off to let it cool anymore since oil pressure stays up.
It should be noted here, that I had oil analysis done after every oil change. Blackstone Labs. All came back perfect: Stock car 0w20, backing off at 118C / Oil/water cooler, 0w20, backing off at 118C / 5w30 C3 no backing off.
I dont drive the car in winter so 5w30 doesnt bother me for cold starts and I like having that extra cushion on pressure.
My advice, an oil/water cooler certainly won't hurt and will definitely help with winter start-ups. But will it do enough to cool in the heat? Only your driving conditions will decide this. If it doesn't, summer/winter oil viscosity can be adjusted. If your planning on keeping the car for a while oil analysis is good for piece of mind.