My thinking on this is simple. I buy the best oil money can buy because this car is not a DD for me. I only change the oil once a year.
I've run Redline in other vehicles in the past and I've never had a reason to doubt it's quality.
Troy Jeup recommends Redline 5w50, and he's built more S85 and S65 motors than anyone else in the USA. Good enough for me.
https://www.m3post.com/forums/showthread.php?t=1592340
From my research, there are plenty of good grade III, IV and V base stock oils. But true full-synthetic, grade V ester formulas are the best oils without any compromises (redline and motul). Expensive, but so is a motor...