I use BMW brand synthetic since I buy it by the case whenever I pick up parts for my 635CSi. Its rebranded Castrol Syntec 5W30, but it is the European formula, ie fully synthetic, not the wannabe synthetic that Castrol pushes here in the states.
Sean
SPOON!
99 Countour SVT (for sale)
02 Jeep TJ
86 BMW 635CSi (for sale)