What Is Antifreeze? (And What Does It Do?)

Along with fuel and oil, your vehicle needs antifreeze to keep the engine running smoothly.

Helping your engine to run at the right temperature – no matter the weather – antifreeze is an essential fluid your vehicle needs, especially in winter.

Read on and find out what antifreeze is, what it does and how and when to replace it.

 

 

What Is Antifreeze?

Antifreeze is a concentrated liquid, made up of ethylene glycol or propylene glycol, that is added to your car’s engine cooling system.

It is most useful in winter but can offer protection all year round.

Antifreeze and coolant are terms often used interchangeably to describe basically the same thing – with coolant being a diluted form of antifreeze with the addition of additives (e.g. corrosion inhibitors).

The main difference between the two is when they are most effective.

Coolant protects your engine from overheating throughout the year, but coolants with a higher proportion of antifreeze are designed to give added protection from freezing in the winter. 

 

What Does It Do?

Antifreeze stops the water in your engine’s cooling system from freezing under normal cold weather conditions when the engine is switched off. 

Without antifreeze, ice could form in your car’s pipes in winter, causing potential engine damage.

It can also raise the boiling point of engine coolant and prevent it from getting too hot and boiling inside the engine.

Antifreeze protects your car’s hydraulic circuit from wear and tear, and the pipes from bursting due to expansion.

 

What Is It Made Of?

Antifreeze can be made of ethylene glycol or propylene glycol.

These are the same base ingredients as those in coolant, which is usually 50% antifreeze.

Ethylene glycol is highly toxic and is more commonly used in older cars.

Propylene glycol is far less toxic and is widely used in modern cars.

 

What Type of Antifreeze Is in My Car?

You can refer to the owner’s manual for your vehicle to find out which type of antifreeze your car needs.

Cars made after 1998 normally need antifreeze that uses silicate-free, organic acid technology (OAT).

Cars made before 1998 tend to need non-OAT based antifreeze that does contain silicate.

There are several different types of antifreeze, so it is essential you use the right kind for your make and model.

 

What Do the Different Antifreeze Colours Mean?

Antifreeze comes in a range of colours and names, and each manufacturer uses a different type of antifreeze.

Whilst the colours are more of a marketing tactic than anything else, they can help you choose the right one for your vehicle.

The different colours are intended to clarify which type of antifreeze is currently in use in the vehicle.

Due to the different chemical make-ups of different antifreeze mixtures, mixing different ones can lead to chemical reactions that you definitely want to avoid.

 

Which Antifreeze Should I Use in My Car?

Your car is designed to use a specific type of coolant with a specific freezing point.

It won’t work properly if you mix two or more different types.

The main types of antifreeze are HOAT, IAT, and OAT, and they all work slightly differently.

HOAT - Hybrid Organic Acid Technology. A form of antifreeze with an extended lifespan. It is created by mixing the other two forms of antifreeze together.

IAT - Inorganic Acid Technology. An older form of antifreeze, commonly found in older cars. Made with ethylene glycol and usually highly toxic.

OAT - Organic Acid Technology. The common antifreeze found in modern cars, it provides high-temperature protection for aluminium. Made with propylene glycol and much less toxic.

 

The information below offers a rough guide on the most common colours used by popular manufacturers.

Please check your vehicle handbook for specific advice on which antifreeze to use in your car.

 

Ford

Ford recommends using Motorcraft antifreeze.

There are different colours to use depending on how old your vehicle is:

• Pre-2002 = Fluroescent Green
• 2002-2010 = Yellow
• Selected 2009-2012 = Dark Green
• 2012-Present = Orange

 

BMW

All BMW vehicles use a blue HOAT antifreeze with no nitrates or phosphorate.

 

Mercedes-Benz

Mercedes use a HOAT antifreeze.

It is blue for vehicles registered before 2014 and pink for vehicles registered after 2014.

 

VW, SKODA, Audi & SEAT

As these brands are all owned by the Volkswagen Group, they all use the same type.

The VW Group recommends using an anti-phosphate, anti-nitrate and anti-phosphorous antifreeze.

This can be either:

• G11 (Blue or Blue-Green)
• G12 (Red or Pink)
• G12+/G13 (Violet)

 

Renault, Peugeot & Citroen

All three French manufacturers use Type D antifreeze. This is green in colour.

The only exceptions are for Peugeot 107 and 108 1.0 essence models and Citroen C1 I and IL 1.0 essence models.

If you own one of these, check your vehicle handbook for the specifics.

 

Kia

Green is the factory fill colour for Kia vehicles.

 

Vauxhall, Fiat

General Motors own both manufacturers, so they use the default GM type.

This is generally red but can also be orange.

 

Toyota

Toyota vehicles use either red, orange or pink antifreeze.

 

Nissan

Blue is the factory fill colour for Nissan vehicles. Some pre-2009 models may need green antifreeze.

 

Hyundai

Hyundai vehicles can use G11 (Blue or Blue-Green), G12 (Red or Pink) or G12+/G13 (Violet) antifreeze.

 

Honda

Honda vehicles have used blue antifreeze since 2004 and green pre-2004.

You can put blue on top of green but not the other way around.

 

MINI

MINI vehicles use a blue HOAT antifreeze with no phosphates or nitrates.

 

Mazda

Mazda vehicles now use a green FL22 antifreeze.

This is compatible with previous Mazda models.

 

If your manufacturer has more than one colour available, you should always refer to your coolant reservoir.

Use the same colour liquid that's already in it.

 

What Happens When You Run Out of Coolant?

If you try to drive a car without coolant, it will likely stop working within a few minutes.  

You could do serious damage to the engine if you continue to drive without coolant – making the need for a full engine replacement a real possibility.  

Your vehicle could overheat, and you could experience poor fuel economy and a loss of acceleration.  

 

Where Can I Buy Antifreeze?

You can buy antifreeze at certain supermarkets and auto parts and supply stores.  

You can also buy pre-mixed engine coolant, which is a ready-to-use solution of antifreeze and water.

 

When Do I Need to Replace Antifreeze?

Many quality coolants have antifreeze properties as standard – as they are a diluted form of antifreeze – but they don’t offer enough protection when the weather turns really cold.  

You can use coolant with a higher proportion of antifreeze to protect your car’s engine all year round, but it is most useful during winter.   

You should change your antifreeze every 2 to 5 years or every 30,000 miles - whichever comes first. 

You can check the vehicle handbook to determine the correct interval for your car.

 

How Do You Prepare to Change Antifreeze?

As coolant and antifreeze mix together, you must change them together as well.  

You should only change yours if you feel confident and have the skills needed to do so.  

Before you begin, you should: 

• Wear gloves and goggles  
• Keep antifreeze away from children and pets 
• Fill the reservoir mostly with coolant 

As antifreeze is highly corrosive – even the non-toxic propylene glycol – you must wear gloves and goggles.  

Make sure that you have water to hand to rinse off any spills if necessary.  

You must keep antifreeze away from children and pets, who may try and drink it as it has a very sweet smell. 

As coolant needs antifreeze properties, you mustn’t add antifreeze on its own, as you won’t be able to protect your car in all conditions.  

Antifreeze alone will not transfer heat away from the engine, so you mustn’t add it on its own. You won’t be able to protect your car from overheating.   

Check the label on the bottle carefully before you add any liquid.  

The engine needs to be cold as it boils while the engine is in use and could scald you or cause damage to the radiator block if you change it whilst its warm, so wait at least 2 hours. 

 

How Do You Change Antifreeze?

To change your antifreeze, you must raise the front of your car on a jack, placing jack stands beneath the vehicle.  

Lower it into place, taking care to place chocks behind your back wheels.  

This can stop the car from rolling backwards.  

Remove an underbody shield – if you have one – and place a container under the radiator and undo the drain valve.  

You can refer to your vehicle handbook to locate it.  

Flush the system as many times as necessary to remove all the old coolant.  

Make sure that you find the reserve tank, remove it and drain any remaining coolant as well.  

Put the tank back in place and replace the drain valve.  

Refill the system with the correct type of antifreeze.  

Make sure you don’t fill past the maximum line.  

You may need to run the engine briefly, top up the coolant, replace the radiator cap and then run the engine again until the cooling fan turns on.  

Check the coolant levels again and top up if needed.  

 

How Do I Dispose of Antifreeze?

You must dispose of used antifreeze at an official disposal site, which you can usually find at a local recycling centre.  

Before you change your antifreeze, make sure that you know where your nearest disposal centre is and that you can transport it there securely.  

Alternatively, you can book a coolant change appointment at a garage near you.  

A professional mechanic will follow the same process as outlined above, using the correct type of antifreeze for your vehicle and checking for any leaks.  

 

 

Be sure to book an appointment if yours looks brown, is a different colour than expected or has lumps floating in it.