Tech Talk

Coolant colour confusion

There’s plenty of confusion in forums these days about the colour of heavy-duty coolants. Does it indicate anything about the chemical make-up of the coolant or is it just a brand to brand thing?

In this article, we’ll clear the air and help you understand key requirements to ensuring optimal health of your engine’s cooling system, year in, year out.

Head chemist and coolant expert Mike Hudson, from Cummins Filtration, helps answer some of these questions.

First thing’s first, what does coolant do?

Put simply, the role of coolant is to transfer extreme heat generated by the engine, to the radiator, where it is expelled into the environment. It is then circulated by the water pump, back to the engine, to repeat the same process over and over again. Coolant also carries with it additives which prevent corrosion and cavitation of the engine and its components, as well as providing anti-boil and antifreeze properties.

Can I just use any old coolant?

If a quality coolant is not used, the risks to the engine include overheating, corrosion and cavitation. These problems can cause critical damage, leading to expensive repairs and equipment downtime, which consequently leads to lost revenue for your business.

What should we look for in a coolant?

First and foremost, choose a good quality coolant from a reputable brand and check that it has been tested to, and meets, a heavy-duty coolant standard. One such internationally recognised standard is the ASTM D6210, and coolants that meet OEM standards are even better. In terms of the coolant’s properties, it should have good heat transfer abilities, a higher boiling point and lower freezing point than water. It should also prevent corrosion and erosion, resist foaming, be compatible with cooling system component materials, be compatible with hard water, resist sedimentation, and be chemically stable. Other considerations include the life of the coolant and its maintenance requirements.

Which colour coolant is the best?

The truth is colour doesn’t mean anything.

In days gone by, the colour of coolant was determined by the types of chemicals used to prevent corrosion, meaning once upon a time, you could tell a lot about a coolant by its colour.

Older coolants that used Inorganic Additive Technology (IAT) were usually blue or green. These types would normally have to be changed roughly every two years.

In the 2000s came Organic Acid Technology (OAT) coolants, whose chemical make-up offered better protection for cooling systems and extended the life of the coolant. These coolants were usually orange or red and offered a five-year or 160,000km change interval.

There are also coolants which are a blend of IAT and OAT chemicals, and these were therefore named ‘hybrids’ (HAT) and were typically yellow or green – but not always.

Nowadays, we can’t rely on the colour to tell us about a coolant’s chemistry or performance. Coolant marketers and OEMs have adopted their own tiered approach to differentiate their products, meaning colour can no longer be used as a guideline to a coolant’s properties.

For example, PGPlus, a hybrid, lifetime coolant with 250,000km or 4000 hours service intervals, is dark blue.

And PGPlatinum, an organic, lifetime coolant which requires no service thanks
to its superior additive package, is red.

Is there a legal standard for coolant colours?

These days, there’s no legal standard for a coolant manufacturer to use a certain colour, so it’s not easy to know what chemicals are in the coolant just by its colour.

How should coolant be maintained?

Every brand of coolant requires different levels of maintenance. Some coolants, such as Fleetguard’s OAT coolant and PG Platinum are lifetime, meaning they don’t need to be changed over the life of the engine, others such as those containing nitrite used for cavitation protection require additive top-ups, as the additives within them deplete over time. Fleetguard’s PGPlus is an example of this.

While some coolants are compatible with others, changing the chemical balance in the cooling system can be detrimental to its performance, so mixing different types of coolant is not recommended.

All coolants, no matter the type, colour or brand should be tested twice a year to ensure they are maintaining the correct chemical composition and concentration.

For more information about coolant and cooling system maintenance, visit

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