My experiences with piston engine airplanes with a oil temp gauge and talking to oil company representative is that most non synthetic petrroleum based lubricants are good to 275 F before they start breaking down. Most standard brand ATF have a additive that starts to change colors from red to brown at 275 and is black by 325F My airplane had a oil cooler thermostst and it ran righ at 190F in straight and level flying summer and winyer, it would get up to 230 F in the summer taking off from Phoenix aggresively (2000 Ft per mintue ) to climb out of the heat.
I had a oil temp, tranny temp and water temp on my old Duster, non filled block making north of 650 HP with a roller cam oiling the valve springs full time would see about the same oil temps as the water temps. I did take the oil temp readings at the back of the block where the oil pressure is taken from so maybe that had something to do with that reading
As long as your below 275F oil temps. your fine
Most synthetics lubricants will run up to 500+ F before starting to fail according to Mobil Oil techs. IHTHs