The only motor oil I buy and change is the Castrol Syntec 0W-30, and that's put in for the "in-between" services that we do ourselves. Unfortunately with the timing and the way seasons work, the X3 always gets the 0W-30 mid-winter and it uses it thru the summer until early fall, when it gets the BMW-paid oil change.

However, the 325i sport is on the preferred track; oil was changed 2 weeks ago ourselves and the slightly thinner 0W-30 will take us thru the winter.