Understanding the Different Types of Engine Coolant
July 20, 2026
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Whether you drive a family sedan, a hard-working 4WD, a commercial vehicle or a performance car, engine coolant plays an essential role in keeping your vehicle operating efficiently. While many people know coolant helps prevent engines from overheating, fewer understand that there are different types of engine coolant designed for different vehicles and operating conditions.
Using the correct coolant is important for protecting your engine, radiator and cooling system components. Choosing the wrong type can reduce performance, shorten the life of cooling system parts and, in some cases, lead to costly repairs.
At Red Devil Radiators, we understand how important it is for Australian drivers to have reliable cooling system performance, especially in our demanding climate. Here’s what you should know about the different types of engine coolant.
Engine coolant is a specially formulated liquid that circulates through your vehicle’s cooling system. Its primary job is to regulate engine temperature by transferring heat away from the engine and releasing it through the radiator.
Modern coolants do much more than simply cool the engine. They also:
Because modern cooling systems are built using a variety of metals and materials, manufacturers develop coolants with specific additives to suit different engine designs.
Not all cooling systems are the same. Vehicle manufacturers use different metals, seals and engine materials, requiring coolant formulations designed to provide the best protection for each system.
While coolant colours can provide a general indication of the type used, colour alone should never be relied upon when selecting coolant. Manufacturers often use different colours for similar formulations, making it essential to follow your vehicle manufacturer’s specifications.
IAT coolant is one of the traditional coolant formulations found in many older vehicles.
It contains corrosion inhibitors designed to protect metal components and typically requires replacement more frequently than newer coolant technologies.
IAT coolant is commonly associated with older Australian, American and classic vehicles where cooling system designs differ from today’s modern engines.
Organic Acid Technology, commonly known as OAT coolant, is widely used in many modern vehicles.
Rather than relying on traditional corrosion inhibitors, OAT coolant uses organic acids to protect cooling system components over a longer period.
Benefits include:
Many European manufacturers specify OAT coolant, although it is also used across numerous Japanese and Australian vehicle models.
HOAT coolant combines elements of both traditional and organic acid technologies.
It provides long-lasting corrosion protection while offering enhanced protection for mixed-metal cooling systems.
Many modern vehicles use HOAT coolant because it offers excellent durability while maintaining compatibility with a wide range of cooling system materials.
POAT coolant is commonly used by many Japanese and Asian vehicle manufacturers.
This coolant formulation provides excellent protection for aluminium engines and is designed to meet the cooling requirements of many modern passenger vehicles.
Brands such as Toyota, Honda, Nissan, Subaru and Mitsubishi often specify variations of phosphate-based coolant formulations.
Si-OAT coolant is frequently specified by European manufacturers and newer model vehicles.
It combines organic acid technology with added silicates, providing rapid protection for aluminium components while maintaining long service intervals.
This formulation is increasingly common in late-model vehicles where manufacturers require advanced corrosion protection and high-temperature stability.
Engine coolant is generally available in two forms.
Premixed Coolant
Premixed coolant has already been diluted with demineralised water and is ready to use.
Advantages include:
Concentrated coolant must be mixed with demineralised water before use.
This option offers greater flexibility but requires careful preparation to ensure the correct coolant concentration is achieved.
Every vehicle manufacturer designs their cooling system around a specific coolant specification.
Using an unsuitable coolant may reduce corrosion protection or shorten the lifespan of important cooling system components.
Following manufacturer recommendations helps maintain:
Australian vehicles often operate in demanding conditions.
High ambient temperatures, long-distance travel, heavy towing, stop-start city driving and off-road adventures all place additional demands on the cooling system.
Using the correct coolant helps ensure the cooling system continues to perform efficiently throughout the year, regardless of driving conditions.
Routine cooling system maintenance is an important part of overall vehicle servicing.
Regular inspections allow technicians to assess coolant condition, inspect hoses and fittings, evaluate radiator performance and ensure the cooling system continues operating as intended.
Professional servicing also provides an opportunity to confirm the correct coolant is being used and that it remains in good condition.
Understanding the different types of engine coolant helps drivers appreciate the important role coolant plays in protecting modern engines.
With today’s vehicles using increasingly advanced cooling systems, selecting the correct coolant is just one part of maintaining reliable engine performance and long-term vehicle health.
At Red Devil Radiators, our experienced team works with cooling systems across a wide range of passenger vehicles, 4WDs, commercial vehicles and performance cars. Whether your vehicle requires routine cooling system maintenance or expert advice, we’re committed to helping Australian drivers keep their vehicles performing at their best.
Does coolant colour tell you which type of coolant to use?
Not always. While coolant colours often indicate a particular formulation, manufacturers use different colour standards. Always follow your vehicle manufacturer’s specifications rather than relying solely on colour.
How long does engine coolant last?
Service intervals vary depending on the coolant type and the manufacturer’s recommendations. Some modern coolants are designed to last significantly longer than older formulations.
Can different types of coolant be mixed?
Mixing different coolant formulations is generally not recommended unless the manufacturer specifically approves it. Using the incorrect combination may reduce corrosion protection and overall cooling system performance.
Is coolant only important during summer?
No. Coolant protects your engine all year round by regulating operating temperature, preventing corrosion and helping maintain efficient cooling system performance regardless of the season.
Why do manufacturers recommend different coolants?
Different engines use different metals, seals and cooling system designs. Manufacturers specify coolant formulations that provide the best long-term protection for those specific components.
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