Coolant Liquid: What do the different colors mean?

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Every internal combustion engine needs an optimal temperature for its efficient operation. The cooling system ensures this optimal engine operating temperature, without which the engine would quickly overheat and seize.

There are several ways to cool the engine, but when it comes to liquid cooling, the cooling system logically needs coolant liquid to function properly.


How does Coolant Liquid work?

The coolant liquid dissipates heat into the air through the radiator. It is a simple cycle - the head and cylinders have a double wall, forming a shell filled with cooling liquid. After it is heated, it flows into the cooler, cooled by the flowing air, and returns to the jacket again.

In the summer, we use distilled water as a coolant; in winter, it's antifreeze. However, the coolant must also fulfill a protective role, so it contains additives. It is therefore supposed to protect the metal parts of the cooling system from corrosion and the rubber parts from cracking and aging, but it must have a sufficiently low freezing point.

What does Coolant/Antifreeze Liquid contain?

The antifreeze consists of 92% mono ethylene glycol, which prevents the liquid from freezing, raises the boiling point, and lubricates the water pump. 2% of the concentrate is water, and the remaining 6% is made up of additives, which have the following composition:

1. Corrosion inhibitors

They protect metal parts that come into contact with the coolant from corrosion.

2. Dispersants

They prevent the formation of scale.

3. Stabilizers

They prevent the precipitation of mineral inhibitors. So they keep them dissolved in the coolant.

4. Anti-foam additives

They prevent the foaming of the cooling liquid, which could cause aeration of the cooling system.

5. pH raisers

They prevent the oxygenation of the cooling liquid. As the pH decreases, the acidity increases, which increases the tendency to corrosion. Acidic liquid corrodes aluminum and eats the engine from the inside.

6. Alkalinity reserve

This is the name given to the property achieved by pH raisers and inhibitors, which protects against damage to the seal and bearing surfaces of the cylinder head.

7. Dye

It can be red, purple, blue-green, or yellow.

However, every coolant loses its properties because its ingredients gradually evaporate or change their chemical composition. Therefore, it is necessary to regularly check and change the coolant, especially before winter, when it is important to measure the freezing point.

When replacing or topping up, use the correct type of coolant. Individual types of coolant are immiscible, but to make sure people aren't confused, different fluids are distinguished by color. Liquids of different colors should not be mixed, while liquids of the same color can be mixed.

Designation and distribution of coolant:

  • G10 YELLOW - is an antifreeze suitable for older engines whose cylinder heads are not made of aluminum alloys.

  • G11 BLUE-GREEN - is an antifreeze mixture suitable for newer engines with aluminum alloy cylinder heads.

  • G12 RED - is a high-quality and modern antifreeze that is highly gentle on metals, plastics, and rubber seals. It is intended for new cars with aluminum alloy cylinder heads.

  • G12+ PURPLE - differs from G12 only in a different color.

  • G13 PURPLE - is an antifreeze suitable for new cars, but it can replace any antifreeze in older cars as well

  • G13 provides metal parts with very high protection against corrosion.


Coolant should be changed every 3 to 4 years because it loses its properties over time. There are many coolants on the market, but you need to choose the right one and not just go by the lowest price because low-quality coolant liquids can quickly degrade and pollute the radiator and the entire cooling system of the car.