I've done some reading, but I can't really decide on what oil i should use in my 535i. I've always ran 10w-30 in my m20 525 and it was just fine, however from what I understand, the m30 likes it a little thicker. What should I use? 10w-40? 15w-50?

I'm in KY btw ... summers are generally 85-105 degrees and winters around 0, sometimes dropping to -10 or so.

And is there any benefit or negatives to using "high mileage" oils (as far as dino oils are concerned)?

Thanks all in advance, and sorry for sounding like a novice here, but I genuinelly can't decide what to put in the car.