Methanol!...at the gas & electric company where my dad worked,they would buy 55 gallon drums of it to use as washer fliud (diluted with water) and also used it in gas tanks for dry-gas to remove water from the fuel...
Some washer fluid I have bought that said it was rated for -20 was frozen solid at 22 degrees last winter-it was the orange stuff,I wont buy that crap again--the 99 cent stuff at a drugstore never froze on me !!..