Good list. Agree with most of it. My opinion on Pennzoil - The used oil analysis don't lie, agree with wear. The dispute is over cleanliness. I feel this falls under your Castrol comments, mostly marketing. There simply is no proof other than website claims and my own results. Using PP and M1 there is no difference in cleaning power. Mobil 1 High Mileage is far better than both for cleaning. Trying PU shortly. The other reason I suspect marketing is Pennzoil's history. For decades cleanliness was the issue with Pennzoil. A perception any marketer wants to change.