The Coolant Oil is used as a coolant, typically to remove surplus heat from an internal combustion engine. The hot engine transfers heat to the oil which then usually passes through a heat-exchanger, typically a type of radiator known as an oil cooler. The cooled oil flows back into the hot object to cool it continuously. Much like oil, coolant serves the basic function of transferring heat and adding antifreeze protection. Coolant Oil is used to cool down the engine so the entire system does not overheat. Oil is a thicker substance that lubricates the parts in the engine to keep them working properly and limit friction within the engine.