In the “good old days”, meaning the 1940’s through the mid 1950’s, we had two types of antifreeze. There was permanent antifreeze and an antifreeze strictly for winter use. DuPont’s permanent antifreeze was called “Zerex” and the non-permanent antifreeze was called “Zerone” As I remember, the Zerone would boil at 180 degrees. I think the windshield washer fluid may not be too different chemically from the Zerone antifreeze. The Zerone was not ethylene glycol as was the Zerex and other permanent antifreezes. I think Zerone was menthanol, but I’m not sure.