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What is antifreeze? What is coolant? Are they the same thing?

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Antifreeze, green.

This is an example of green ethylene glycol based coolant.

photo by Matt Wright, 2009
Definition: Antifreeze, also called coolant, is the colored fluid (usually green or red) found in your radiator. Antifreeze serves a few purposes. The most important and known is keeping the water in your radiator and engine from freezing in cold temps. It also keeps that same water from boiling over in the summer. Radiators are normally filled with a 50/50 mixture of antifreeze and water. The third function of antifreeze, or coolant is lubrication -- it lubricates the moving parts it comes in contact with, like the water pump.

How Does It Work? The key chemical component in today's coolants is ethylene glycol. Mixed correctly, this stuff can keep your radiator fluid from freezing even if the temperature is less than 30 degrees below zero! That's cold. The amazing thing is that it can also keep the same fluid from boiling at as much as 275 degrees F. Antifreeze can really get control of those water molecules!

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