Although the terms ‘antifreeze’ and ‘coolant’ are often used interchangeably, they’re not the same thing. Antifreeze is a liquid that contains either ethylene glycol or propylene glycol, whereas a coolant is a mixture of antifreeze and water.
Most modern vehicles have cooling systems that use a solution of water and antifreeze to maintain a stable temperature and prevent damage to the engine. Antifreeze has to be diluted with water because it’s expensive, and pure antifreeze can actually damage your car.
Pure antifreeze typically has a freezing point of between -18°C and -15°C. The freezing point can be further lowered when mixed with water, making it a more effective coolant.
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Can I use antifreeze instead of coolant?
It’s generally not a good idea to use pure antifreeze instead of coolant. Aside from being more expensive than a water-antifreeze mixture, pure antifreeze doesn’t have the same heat-transfer efficiency as a coolant. In fact, a car can lose approximately 35% of its heat-transfer capabilities, making the engine less efficient and increasing the chance of it overheating. 
Keeping the engine’s temperature at a certain standard level ensures it runs smoothly and efficiently. It also prevents engine damage due to overheating, especially during the summer months. A coolant is much more effective at taking away excess heat from the engine than pure antifreeze.
Another important reason why you shouldn’t use pure antifreeze instead of a coolant mixture is to prevent additives from settling at the bottom of the engine.
Additives contain silicates, phosphates, and nitrates that are suspended in water but can easily settle and accumulate at the bottom. If this happens, the anti-corrosion and other protective functions of the additives will be rendered useless.
Why is engine coolant called antifreeze?
Although ‘coolant’ and ‘antifreeze’ tend to be used to mean the same thing, it’s not technically correct to call engine coolant ‘antifreeze’.
For a start, not all coolants have antifreeze in them. Some cooling systems, such as those found in nuclear power plants, do not contain antifreeze. When antifreeze is mixed with water, the mixture becomes a coolant. Nonetheless, engine coolant is commonly called antifreeze because the latter is also commonly mixed with water.
Why is antifreeze added to a car radiator?
Antifreeze is added to a car radiator to prevent the radiator water from freezing in sub-zero temperatures. This is a common practice in countries located in temperate zones.
As the name implies, the function of a car radiator is to radiate the excess heat of the engine to prevent damage (and possible explosion) due to overheating. The radiator has fins and tube coils that effectively dissipate heat into the surrounding air, away from the engine.
Adding antifreeze to a car radiator is optional in hot, tropical countries as the high temperatures mean there’s no risk of the radiator water freezing. That said, even in tropical climates, adding antifreeze to a car radiator can significantly increase the heat transfer efficiency of the car engine.
Can you mix coolant and antifreeze?
Yes, you can mix coolant and antifreeze, although it may only increase the amount of dissolved antifreeze because the coolant may already contain antifreeze. Car coolants in temperate regions already have antifreeze in them.
This is important not only in terms of preventing the water from freezing, but also increasing the heat-transfer efficiency of the coolant. Neither pure water nor pure antifreeze makes an efficient coolant.
