Antifreeze, also known as engine coolant, is a liquid substance that circulates through an internal combustion engine and draws off excessive heat. The two most common chemicals used for this are ethylene and propylene glycol, both of which have lower freezing points than water (32° Fahrenheit or 0° Celsius). This allows the chemicals to flow freely even under cold winter conditions. Antifreeze also has a higher boiling point than pure water, which makes it ideal for summer use as well.
Internal combustion engines generate a significant amount of heat as part of their normal operations. This heat is eventually transferred to the metallic and synthetic parts of the engine block, which in turn causes friction and expansion. Engine oils and lubricants may reduce the friction, but the heat still needs to dissipate away from the engine. This is where antifreeze enters the picture. A closed system of hoses and a water pump circulates either pure antifreeze or a mixture of it with water throughout the engine block.
The excessive heat is drawn away by the "heat sink" effect of the chemicals. By the time the antifreeze has passed through the entire engine block, it may be near the boiling point of water. This superheated liquid is pumped into a radiator placed in the front of the engine compartment. A combination of outside air and forced air from a fan help to reduce the temperature. The radiator itself has numerous chambers and channels that allow heat to pass through to the outside air as well. As the antifreeze reaches the other side of the radiator, it should be cool enough to re-enter the engine block and start the process all over again.
Not all antifreeze compounds are created equal. Some are intended for regions with extreme temperature variations, while other are formulated for summer months with higher heat ranges. There may also be variations in the ratio of water to antifreeze for optimal operations. Too little antifreeze can lead to boil-overs or a completely frozen radiator. Too much may not harm the car's operation, but it can be too expensive for drivers to use undiluted product all of the time. The chemicals are generally inexpensive, but occasionally there are sudden price spikes as demand rises and supplies run low.
One important thing to keep in mind is the poisonous nature of ethylene or propylene glycol. Antifreeze can smell sweet and look inviting to pets and small children. Drinking it can cause serious illness or even death, so containers should be kept in secured storage areas. If a pet ingests antifreeze, a veterinarian should be contacted immediately for emergency services. It's important to warn children not to drink it because, even if parents store it carefully, neighbors may not be so conscientious.