Antifreeze (coolant)

Antifreeze is a water-based liquid coolant used in gasoline and diesel engines. Compounds are added to the water to reduce the freezing point of the mixture below the lowest temperature that the engine is likely to be exposed. Until the late 1930s, methanol was the most widely used antifreeze. While effective in preventing the coolant from freezing, its low boiling point and low specific heat capacity led to considerably less cooling than water alone. Also, the concentration of methanol would tend to be reduced over time due to its greater tendency to vaporize than the water with which it was mixed. Ethylene glycol became available in 1937 and was marketed as "permanent antifreeze," since its higher boiling point provided advantages for summertime use as well as during cold weather. It is still used today. Most commercial antifreeze formulations include corrosion inhibiting compounds, and a green or blue fluorescent dye to aid in identification. A 1:1 dilution with water is usually used, resulting in a freezing point of -40° Celsius or Fahrenheit. In warmer areas weaker dilutions are used.