Some threads here start with things like "I used blah, blah super duper oil and now I have XX problem" or "By the way I'm using snake oil-100/500 with Seafoam" I take back the Seafoam part, that seems to be the domain of E39 owners.

Something tells me BMW's engineers put some effort into what they recommend and it doesn't make sense to mess with success. Me, I'll stick to the book.

Perhaps some is because of new owners who never had an owners book to referrence and are swayed by ads or the nit-wits at Greasy Lube.