Originally Posted by Jason911
Also in Wisconsin, I had -24° last winter on one of my outdoor cams. And that was without windchill. My washer fluid is -35F, and I still see icing/freeze up.
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If your vehicle is moving, the fluid will evaporate, and that can cool it below the freezing point... plus, the first to evaporate would be any alcohols, so if there's enough of it, the remnant water will freeze.
I doubt the heater or external blanket would truly deal with it 100%, any more than juicing up the fluid with about half pure isopropyl does, but freeway driving in blizzards below zero can put a lot of ice on the vehicle, enough the sensors get coated, the ACC takes the day off, etc.