I have read a few things on this issue. One being that some are putting
0W-40 oil in their X for the winter. Also if you drive short distances in cold temeratures Try using the sport mode shifting and keep the rpms up to make the motor run hotter and burn more condensation than usual. Apparenlty bmw made a revised kit for their oil separator that comes with a insulating jacket of some sort. Or simply put it in a garage for those really cold nights? That might help. Last winter I hasd no problems, now this winter I have no garage and its gone twice on me within a month.... Go figure!