Actually, that makes ME wonder: how does scum grow in a toxic methanol solution?
Because washer fluid is used so rarely, the alcohol in the washer fluid evaporates away, turning it into a jug of lukewarm stale water. Last winter there was some frost on the windshield of my pickup and I thought I’d try to just use the washers to clear it. All I did was add a layer of frozen mess to my windshield.
Salt on the roads? We use sand here in Western Washington, on the 3 or 4 days that it snows. It’s always raining here though, which is probably why we don’t need as much washer fluid. Rain, mother nature’s washer fluid and it’s free.
A few years ago I noticed chemical anti-icer being put on the roads in anticipation of freezing weather. Since it contains molasses I can see why it makes a mess of the windshields. http://horsesass.org/washington-dot-screws-de-icer-industry/
@ok4450 growing up I spent my summers on a farm in Eastern Montana. You didn’t need to look outside to see if the strip next to the house was fallow or planted, just run your finger along the counter.