(1) Water additive. Any compound that lowers the freezing point of water. Both sodium chloride and magnesium chloride were once used, but their extreme corrosive properties made them a liability in automotive cooling systems. Methanol requires only 27% by volume for protection to −17.7C. Due to its tendency to evaporate rapidly at operating temperatures, its flammability, and its low boiling point (63.9C), it has been replaced by glycol derivatives which are relatively noncorrosive, nonflammable, have very low evaporation rates, and are effective heat-exchange agents. A concentration of 35% protects against freezing to −17.7C. Ethylene and propylene glycol antifreezes can be carried in an automotive cooling system for several years without damage, and are satisfactory coolants at summer operating temperatures. Methoxypropanol has been introduced as an antifreeze-coolant for diesel engines. (2) Gasoline additive. A proprietary preparation, TM “Drygas,” consists of methanol, isopropanol, or mixtures of these, that lowers the freezing point of water enough to inhibit ice formation in feed lines and carburetors. It is added directly to the gasoline.
