What oil are you using? The lifter and top end of the engine is the last to get oil as it has to be pumped up to the top on startup. The BMW LL01 (US) standard recomends Mobil 1 0w-40 or German Castrol 0w-30. Anything too thick and your going to have ticking from the lifters as they get oil starved. I run 0w-40 even in the winter.