I'm out of windshield washer fluid, and the lows (very unusual here) are going to be 20F. I think I may have water or very watery washer fluid, since I haven't refilled the washer fluid since the summer, nor have I winterized my car yet. I'm worried about freezing and damaging the plastic washer container. Would dumping ammonia in there help lower the freezing point? Is that fairly okay to put in there?