I used to make lubricating oil base stocks for one of the major oil companies.
I wouldn't get hung up on Castrol, Shell or Mobil spend far more money on lubricant technology than Castrol ever has.
I may well be wrong, but, I don't believe BMW ever actually used Castrol, it was just a marketing deal. I think Fuchs was initial fill in the factory and every BMW dealer I have used was using Shell for servicing.
Mobil 1 would be my choice and is what I have always used.
Ian
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