Testing Coolant Condition and Summer Mixture

Coolant Mixture

What is the purpose of coolant?


Coolant is the fluid used to transfer heat from the engine to the radiator. The 2 main components of the mixture are distilled water and glycol. There are also additives that protect rubber seals and inhibit corrosion.

Coolant has excellent thermal absorption and it’s a liquid over a wide temperature range. As the freezing point of distilled water is impractical for automotive use, it is mixed with glycol which gives it the “anti-freeze” properties. But glycol has a low boiling point. When they are combined, they offer the best balance.

The mixture is able to sustain liquid form through extreme cold temperatures. However, the boiling point of coolant is lower than that of water alone. But keeping it pressurized raises its boiling point. The normal operating temperature of the engine is a balance between optimal combustion chamber temperature and adequate cooling headroom.

The engineers juggle many parameters when designing a car. Engine performance and coolant characteristics directly affect the cooling system design. Much like motor oil, the coolant is a critical component. Even tho it is a passive component and doesn’t need refills, it has a service life.

The coolant doesn’t exactly wear out and won’t lose it’s ability to transfer heat. But the additives can break down. Also, over the extended life span the mixture might change. The distilled water does evaporate so it is a good idea to test the mixture composition.

Summer Formula


For some drivers, the option to increase the boiling point exists. The typical coolant is half distilled water, half glycol. However, it is possible to mix a summer coolant formula. The only downside is that it will freeze earlier. For most, a sudden -30 C is unlikely to happen so the risk is minimal. However, freezing the engine in the winter time could be a costly mistake.

For a summer formula, use a minimum of 30% glycol. Straight distilled water will damage seals and cause corrosion. As water has better thermal characteristics than glycol, it will also help with heat transfer. But the effects are minimal and likely won’t solve an overheating issue. The biggest safety factor is raising the unpressurized boiling point. At the same time, installing an adjustable fan controller to increase airflow will help dissipate heat faster.

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