From what I've researched, it looks as if these oils 5w-50, 15w-50 and 20w-50 oils are definitely higher than Xw-20/Xw-30 in zinc, but what else are they higher in? Are they higher in detergents as well or it's about the same? I'm sure alot of factors vary between brands, but is there a rule of thumb here? Also, I'm looking at mixing some 5w-50 with some 0w-20 (50/50 mix and both are Quaker State full synthetic) sometime in the near future. Any thoughts on that?