What I'm gathering here is oil debates devolve into a lot of science and personal preference plus added confusion of dealers, manufacturers and everyone else in the chain changing their minds?
Ok, whatever, but the basic simple option to the expensive ($8.50 a quart) BMW branded 10w40 I pick up at the dealership is to go with Castrol 10w40? This is recommended in the service manual? Make sure it is motorcycle specific formula though right?
Like this stuff?
Oh and for what it's worth, even buying the BMW branded oil at my dealer, the parts guy or service tech has interchangeably sold me the 10w40 or 10w50. I queried them on that and they both said it doesn't make a difference.