I wonder what could be in a tablet that'll prevent a gallon of water from freezing. Most windshield washer fluids use a ratio of methanol and water. Some add isopropyl and ethylene glycol to keep it from freezing. How is a tablet going to work when the amount of water is 100%? Some of us blend our own windshield washer fluid. But, my days of finding a gallon of methanol for $3 is over...
I also forget about HEET.... 100% methanol and ISO-HEET is 100% rubbing alcohol.... but still $25 a gallon. Haven't used it since the introduction of E10. Available source is another excuse to install the water/meth injection.... and go back to high btu 87 regular in place of the pricey 93 octane premium! Hard to find windshield washer fluid that isn't loaded with all kinds of bug removing detergents, colorings, all with unknown water/meth ratios, windshield rain repellent coatings, and glycols. Will also be considering a misting kit for the running engine IVD cleaning in place of canned spray IVD products like CRC/STP/Lucas/Seafoam.... Paint lacquer thinner is another option since the SDS list seems to be a acceptable recipe for gasoline engines. Ethanol isn't cheap unless you're making your own 'shine.
Its pretty sad if you go out and buy a brand new car, and now its winter, and you don't use windshield washer much, and you find out its only water.