I have some recollection of being scolded in some other thread when I said "do what the manual says".5w50 is the ideal viscosity according to the owners manual, it covers all temp ranges.
My point being the people who designed the product knowing better than the keyboard pounders.
I used a Mobil 1 product in my '05 RR; the manual said some specific A3/B3 or something, and the Mobil 1 0W-something was the only (readily available) oil that met the spec.
But wtf do I know, I just did what the manual said.