Originally Posted by SteveC
Water doesn't give a damn about windchill...only the temperature matters, so your screen wash froze at -9ºc. My experience with pre-mixed garage washer is that it freezes in the jets and pipes because its mainly water, dye and some detergent and alcohol. Even heated sprayer jets don't help because the mix itself freezes in the pipes leading to the jets
Apart from the danger of freezing, the wrong windscreen wash formulation can harbour dangerous bacteria like Legionella, damage your car's paintwork, block the spray jets and/or block the filter. Given that the BMW formulation does non of these things when used at recommended concentrations of as little as 5:1 it really is false economy to use anything else IMO.
It was -11°c when I left my house and it was working. Then 15 minutes later it blocked. You sure extra air doesn't make it colder?