Why 20w50? That is awefuly thick oil for an engine designed for 10w30. Thick oil may protect better, but unless the clearances are large enough it won't flow very well, and will actually protect less. Unless the engine has been rebuilt for this, I wouldn't run it. It will also cause more drag on the oil pump that will rob the engine of power, and could even break the oil pump shaft. So if you are going to run it, make sure you have an upgraded oil pump shaft. Thin oil may "protect less" but it will flow better, which will result in better protection, and will free up more HP. Oil starvation is more of a concern than anything else. Also, consider the worse time for wear is on start up, where the oil has drained down, it's going to take a lot longer for that oil to reach moving parts especially when cold. Unless your engine is built for 20w50, I would go a little thinner.
I run 0W40 Mobil 1. Super thin when cold, just a bit thicker when hot. I ran different oils before between 10w40 and 5w30 as well as 10w30. I read a lot of reviews on the 0w40M1 from different sourses. With the 10w40, the engine seemed to run well once warm and I had little noise, but it was loud on start up. The 5 and 10w30's were better at low RPM and cold start but I could always hear valve noise in upper RPM's. Now with 0W40 I am very impressed. Almost NO noise on start up, instant oil pressure, and it stays up there, and no high RPM noise at all, engine runs the best on this stuff.
Also, for protection, look into the zinc content of the oils.