The Castrol Syntec is a thin 5W-30. BMW requuires a thick 5W-30

The genuine BMW 5W-30 is 12.2 cSt viscosity at 100C/212F and exceeds 3.5 cP HTHS viscosity at 150C/302F.

The Castrol Syntec is 9.7 cSt viscosity at 100C/212F and is between 2.9 and 3.5 cP HTHS... Login to read more.