I put a certain oil into the Calculator, the letter starts with a V, and it is a 0W-20 oil, at 255 Degrees this oil has a film thickness of 5.56, I like a film thickness with the number 10 depending on the oil temp.
My Mobil 1 ESP 5W-30 is good up until my 10 number of 226F in my car. Realistically, my oil temp in the car in the sump is probably 210F at the most. I have a riding lawnmower that I use a temp probe after mowing and my Shell Rotella T5 10W-30 was only good up to 226F, that is with my 10 number. I am now using HPL CK-4 10W-40, which is good to about 242F, when I compare the 2 oil's, the temps are about the same to a certain extent. Here is where I need a more realistic oil temp reading, I mow the yard, and then I leave the mower running for a minute while I blow it off, and then I put the mower in the shed and take a temp reading. My 220 to 230 temp reading may not be 100% accurate. HPL 10W-50 would be good to about 264F in an air cooled engine.
I really think it is important to look at oil temps, I once asked a member here what his oil temps were with his Riding Mower, he said 180F, found out he had 1 of those old school John Deere Liquid Cooled engines.