Proper Oil Viscosity Is Crucial. You will notice in this chart below, 10w30 viscosity at 120c/250f is about the same as 5w20 at 100c/210f. Therefore when you use oil at 5w30, you can have the oil temp slightly higher at 120c in order to maintain the same viscosity as 0w20 at 100c.
Ref:
https://www.elephantracing.com/tech-...d-engine-life/
Oil also needs to be over 100c in order to evaporate moisture mixed in the oil.