What is Coolant?

Coolant is a fluid that circulates through your car’s cooling system. Usually a mixture of an anti-freeze anti-boil corrosion inhibitor concentrate that has been diluted 50/50 with good quality water, the coolant absorbs heat from the engine and releases it at the radiator.

The styling of modern cars means that the engine often doesn’t have a lot of space. A high-functioning cooling system is essential to prevent the engine overheating.

Using the wrong coolant for your car could be ineffective or it could damage your engine. Learn how to choose the right coolant for your car with our coolant selection guide

Why is engine coolant important?

Coolant performs three main functions to protect your car engine:

  1. Coolant transfers heat from the engine and releases it through the radiator, keeping the engine at a safe operating temperature.
  2. Coolant generally has a higher boiling point and a lower freezing point than plain water.
    If the water in the engine boils, it turns into a gas, which cannot transfer heat effectively. If the liquid in the cooling system were to freeze, it would expand, potentially breaking and cracking pipes and parts of the engine.
  3. Coolant contains corrosion inhibitors that protect the metal and non-metallic (usually rubber hoses, seals and plastic tanks) parts of the engine cooling system.

Why use coolant and not just water?

There are two key advantages of using engine coolant rather than just water. First, coolant has a higher boiling point than water. This means that when parts of the engine heat up over 100°C when you are sitting in traffic or towing a trailer up a steep hill, the coolant liquid won’t evaporate.

The second key reason to use coolant is that it contains corrosion inhibitors. This protects the components of your engine and cooling system from corrosion. It’s much cheaper to buy coolant and check it regularly than it is to replace major parts of your car engine and cooling system.

What are the different types of car coolant?

There are 2 main different types of car coolant available.

  • Anti-freeze/anti-boil (AFAB) Australian Standard AS2108-2004 “Type A” Coolant which then includes some special formulations for particular uses.
    • Organic Acid Technology (OAT) premium AFAB coolant for general use
    • Hybrid Additive Technology (HAT) AFAB coolant for general use
    • Phosphate-based AFAB coolant (formulated for Japanese & Korean cars)
    • Silicate-based AFAB coolant (formulated for European cars)
  • Corrosion inhibitor Australian Standard AS2108-2004 “Type B” Coolant

What Coolant Should I Use For My Car?

car and radiator coolant

Always check your car manual to ensure the coolant you choose meets the requirements of the manufacturer.

Which coolant for Honda, Hyundai, Kia, Mazda, Mitsubishi, Nissan, Subaru or Suzuki?

For these car models, we recommend using Adrad’s blue phosphate-based coolant designed for Japanese and Korean vehicles.

Which coolant for Toyota or Lexus?

If you drive a Toyota or Lexus, we recommend choosing Adrad’s pink phosphate-based coolant designed for Japanese vehicles.

Which coolant for Ford?

If you drive a Ford built in 1997 or later, use organic corrosion inhibitor; or use organic anti-freeze coolant if your car may be exposed to freezing temperatures.

Inorganic corrosion inhibitor or anti-freeze coolant can be used in Fords built before 1997.

Which coolant for Holden?

If you drive a Holden that was built since 2001, is a turbocharged, Alloytec or V8 Gen III or IV model: use an organic corrosion inhibitor or an organic anti-freeze coolant, depending on the climate where the car is used.

If your Holden was built before 2001 and isn’t turbocharged, Alloytec or V8 Gen III or IV, you can use an inorganic corrosion inhibitor or an inorganic anti-freeze coolant.

Which coolant for Mercedes, VW or Audi?

If you drive a European car built since 2004, choose the silicon-based light-red coolant.

Older European models can use organic anti-freeze or an organic corrosion inhibitor if your car isn’t exposed to freezing temperatures.

If you still aren’t sure which coolant you should select for your car, a radiator technician at your nearest Natrad can give you advice on choosing the right coolant.

How do I top up my car coolant?

pouring coolant into tank

Now that you know which coolant to put into your car, here’s a video guide explaining how to top up your car’s coolant.

You can purchase coolant as either concentrate, which requires you to mix it with high-quality (usually distilled) water or buy coolant pre-mixed, which can be poured directly into the radiator.

Now we’ve covered the basics, here is a more comprehensive guide to the different types of engine coolant:

Anti-Freeze/Anti-Boil (AFAB) coolant (Type A)

Adrad AFAB coolant can be orange or green. Inorganic coolant can be purchased for older vehicles. Most modern cars require organic anti-freeze coolant.


Adrad AFAB coolant supplied by Natrad provides wide temperature protection. A 50/50 mixture will protect your engine at temperatures from -37 °C to 129 °C.


This coolant provides protection against pitting, corrosion and erosion of aluminium, iron, steel, brass, copper and solder alloys. Adrad Type A coolants are phosphate-free, which means that there will be less hard-water scale build-up. By reducing the concentration of dissolved solids from hard water, using this coolant will increase the longevity of water pump seals.


Adrad Type A coolants are free from nitrite, amine, phosphate, silicate and heavy metals such as borate.


Adrad premium organic AFAB Type A coolant is designed to last up to 250,000 km or 8 years for passenger cars.


This coolant meets AS 2108-2004 for engine coolant Type A.


If your vehicle is built after 2001, select an organic anti-freeze coolant. Any vehicle with a turbo/supercharged engine, Holden Alloytec or Gen 3&4 V8 should also use organic rather than the cheaper inorganic anti-freeze coolant.

Anti-freeze/Anti-boil should be used in any car that could be exposed to freezing temperatures.

Corrosion inhibitor (CRIN) coolant (Type B)

Adrad CRIN or Type B coolant is either orange or green. This water-based, glycol-free mixture is suitable for a wide range of cars where freeze protection is not required.


This coolant provides cost-effective engine protection where anti-freeze is not required.


Adrad CRIN coolant provides stable and reliable protection from pitting, corrosion and erosion for metals including aluminium, iron, steel, brass, copper and solder alloys.

The formula in this coolant doesn’t contribute to deposit build-up which can restrict or even block the radiator system. It provides protection for the rubber and plastic parts of the engine and cooling system.


Corrosion inhibitor purchased from Natrad is readily biodegradable. When disposed of at the recommended concentration of 7.5-10% in water, this glycol-free coolant has a low environmental impact and low toxicity to marine and animal life.

Adrad CRIN coolant is free from nitrites, amines, phosphates or silicates (NAPS-free), as required by many car manufacturers. This coolant is free from borate and other heavy metals.


Adrad premium organic CRIN Type B coolant is designed to last up to 250,000 km or 8 years in passenger cars.


This coolant meets AS 2108-2004 Engine Coolant Type B and Ford Engineering Specifications.


This water-based coolant is suitable for vehicles in temperate climates, where anti-freeze isn’t required. It can be used in cars, tractors, on or off-highway trucks and marine applications. Choose an organic corrosion inhibitor coolant for vehicles built since 2001.

Si-OAT coolant

Adrad Si-OAT advanced anti-freeze coolant is based on ethylene glycol and glycerol and contains a durable OAT inhibitor combined with silicate additives (Si-OAT).

This light red or violet coloured coolant is used in the latest high-tech engines where high-temperature aluminium protection is required.


Designed to meet the specifications of modern European vehicle manufacturers, Adrad Si-OAT coolant provides effective anti-freeze and anti-boil protection, particularly for aluminium components.


This high-performance engine coolant provides effective corrosion protection for all engine metals, including aluminium and ferrous alloys. It can be used with confidence in engines manufactured from cast iron, aluminium or combinations of these two metals, and in cooling systems made from aluminium or copper alloys.

Adrad Si-OAT coolant provides excellent corrosion, cavitation and erosion protection for aluminium water pumps.


Silicon-based coolant uses a more environmentally friendly manufacturing process, partially replacing ethylene glycol with glycerol. Adrad Si_OAT coolant is free from borate, nitrite, phosphate and amines.


Adrad Silicon-based coolant is compatible with most other coolants based on ethylene glycol. The cooling system should be flushed and coolant replaced every 250,000 km or 5 years.


Natrad supply Adrad’s silicon-based coolant which meets or exceeds: AS 2108-2004 Type A, ASTM D3306, BS 6580:2010, G11/G12/G12+/G12++, VW TL 774 J (G13).


Silicon-based coolants are specifically designed for European vehicles, including:

Volkswagen, Porsche, Audi, BMW, Mercedes-Benz, Porsche, Skoda, Scania.

P-OAT coolant

Adrad Phosphate-based Organic Acid Technology coolant is designed to meet the performance and chemistry required for Japanese and Korean manufactured vehicles.


It provides complete anti-freeze and anti-boil protection from -37 °C to 129 °C.


Adrad P-OAT coolant provides effective corrosion protection for brass, copper, solder, steel, iron and aluminium through its well-balanced hybrid inhibitor package. The pink or blue coolant acts to stabilise hard water, protecting non-metal parts and preventing premature water pump failure.


Adrad P-OAT coolant is free from silicate, borate, nitrite and amine.


Adrad P-OAT coolant is designed  to last 250,000 km or 5 years in passenger vehicles.


Adrad P-OAT coolant can be coloured pink or blue and meets or exceeds AS 2108-2004 Type A, ASTM D3306, BS 6580:2010, JIS K 2234-2006 Class 2.


Adrad P-OAT coolants are specifically designed for Japanese and Korean vehicles including:

Toyota, Subaru, Kia, Mazda, Mitsubishi, Suzuki, Lexus, Nissan, Daihatsu, Honda, Isuzu.

When does coolant need to be changed?

mechanic servicing engine


Maximum service life is only achieved under ideal conditions. Most coolant will need to be changed every few years. Check your car manual for the manufacturer’s recommended service interval.

If you aren’t sure when your car last had a coolant flush and change, a Natrad radiator technician can test your coolant to determine whether it needs to be changed soon.

Can I just buy the cheapest coolant?

Our supplier has compared the Adrad coolant sold by Natrad with cheaper coolants available.

Laboratory testing reveals that cheaper coolants can contain borate buffers. Most manufacturers specifications do not permit the use of this old coolant technology for environmental and toxicity reasons.

The cheaper coolant tested in the lab contained a higher water content than recommended by international and manufacturer specifications. It also contained 25% lower concentration of organic inhibitors than the Adrad coolant.

This means that corrosion protection offered by the cheaper coolant will not be as effective, particularly for applications like 4WD, commercial vehicles and heavy-duty engines.

If you ever have a question about the right coolant or your cars cooling system, get in touch with a specialist technician for advice or check out our coolant selection guide.