I've traveled for business to NB on a regular basis in the past and it can get pretty cold there but only had issue with rental cars where washer fluid freezes. That only happened some 20 some years ago as some car rental companies back then put water in to save costs. They don't do that anymore for fear of getting sued if someone gets into a accident. But it sounds like as someone said your using summer rated fluid or someone put water in your BMer at some point. You should check with the wife, but be nice about it
