I will get to Castrol and Valvoline oils eventually. This is a test of Warren Distributing which has a niche market for oils like Supertech, AmazonBasics, etc.
I have never heard bad things about Warren Distributing...but I havent seen any dedicated users of their oil either. Ive been told their oils are not bad but dont have any data which clarifies vague statements of good or great.
These days engines are becoming unique. While Penzoil, Mobil 1, etc might make a great general oil it may not be the best for all engines. The turbo Subaru guys seem to think they need a 5W40 HDEO and thus they sell TDT and Delvac at racing places like Summit Racing. So while I have no doubt Penzoil Platinum is great...it may not be great for all engines.