Coolant in its most basic form is a fluid that transfers waste heat away from an internal combustion engine. Without the proper flow of coolant, critical engine parts may degrade, deform, or even crack and fail.
The cheapest and most effective coolant is usually water but it has some major shortcomings. It is corrosive to many metals such as iron, aluminum and copper, and it expands when it freezes, bursting whatever contains it (including radiators and engine blocks). To overcome these problems other chemicals can be added to water to make what is typically called “antifreeze”.
To prevent freezing and bursting we usually add glycol. This chemical is only slightly less effective than pure water at transferring waste heat and, in proper mixtures, can reduce the freezing point of the fluid well below 0 degrees Fahrenheit.
To prevent or inhibit corrosion a wide variety of chemicals are added to the coolant. Each one serves a purpose, protecting various metals or components in the cooling system. Some even protect the coolant itself, inhibiting degradation and the formation of corrosive acids. These “inhibitor” formulations can be quite complex, containing 15 or more different chemicals.
These corrosion inhibitor additives are often the defining or differentiating aspect of the coolant. Different chemistries are used to make Conventional, ELC (Extended Life Coolant), OAT (Organic Acid Technology), Hybrid or several other more obscure types of coolants