saaber1, I found so far M1 0w-40 to be the best of the oils I have tried with Castol Syntec 5w-40 being the worst. Right now I am experimenting with M1 ESP 5w-30 and I clearly hear a difference in the engine. The engine runs significantly quieter compared to all the 40 weight oils I've tried including M1 0w-40. As far as performance, I'm still judging that.
My goal is to prevent 5,000 valve cleanings and attempt to extend it to 15,000 invervals because that is how severe my impact is. I change my oil ever 5,000.