It's important to note that the more obscure an oil is, the better it must be. Advantage German Castrol here, hands down.
Oils which cannot be readily found on the store shelves are the ones to seek out; they are certainly the better choices.
Common oils, which can be found practically anywhere, are of course boring and ineffective and show increased wear metals in UOA's.
That's what makes GC so special, and such a great oil. It's hard to find. Sometimes AutoZone won't even have it on their shelves. Don't laugh, it's been known to happen, and it isn't pretty when it does.
Remember, too, that no watermelon tastes as good as a
stolen watermelon. Not encouraging anyone to shoplift, but I've often wondered how much better the UOA's would look if one were to "liberate" a few quarts of the elixer. Probably at least some better I would think...
Dan