Antifreeze : A liquid used to cool the engine. This is a chemical called ethylene glycol is used in most automotive antifreeze types. Sebacate and 2-EHA (2-ethylhexanoic acid) is used in Dex-cool which is used in most newer american vehicles. G-05 contains benzoate as a main ingredient. Extended life coolant use phosphates, OAT and sebacate. The purpose of antifreeze is to change the boiling point and freezing point of the water cooling the engine. As a bonus, the antifreeze also helps lubricate cooling system parts like the waterpump and thermostat and keeps the cooling system from rusting.