Antifreeze: what is it, colours and how to use

Antifreeze is vital for keeping your car running in the cold winter months. But what is it? And how does it work?

Car maintenance can be daunting and if you've never bought antifreeze before you may be confused by the different colours and types of fluid on offer.

To help you understand antifreeze and why it's important for your car, we've created this guide to explain the different variations and how to put it into your vehicle.

What is antifreeze?

Antifreeze is typically a mixture of water and chemicals, such as ethylene glycol or propylene glycol, which have properties that lower the freezing point.

Antifreeze prevents the coolant from freezing in cold weather, which would otherwise cause it to expand and cause damage to the engine, radiator and the rest of the cooling system.

It also helps prevent overheating by raising the boiling point of the coolant, allowing the engine to operate at higher temperatures.

An added benefit is that it provides corrosion protection by containing additives that protect the engine's cooling system components, such as the radiator, water pump and hoses.

What does antifreeze do and why does my car need it?

Antifreeze prevents your car’s engine from freezing in cold temperatures and from overheating in hot temperatures.

It works by lowering the freezing point and raising the boiling point of the coolant.

A car needs antifreeze to maintain proper engine temperature and protect the cooling system from damage.

By topping it up regularly, it ensures that the engine runs efficiently in all weather conditions.

Is antifreeze the same as engine coolant?

No, antifreeze and engine coolant are not the same – but they do have similar properties and are usually used together.

Antifreeze is a key component of engine coolant, which is a mixture of antifreeze and water.

The coolant regulates the engine temperature, preventing freezing in cold weather and overheating in hot weather, while also protecting the system from corrosion.

• Common breakdown problems – your complete guide
• How to check your engine coolant
• What should I do if my car is overheating?

What do the different colours of antifreeze mean?

There are three main variants of antifreeze available in the UK, which are identified by different colours.

Green antifreeze

Green antifreeze, or IAT (Inorganic Additive Technology) is recommended for older vehicles - those built before 2000 - with more metal components in the engine than later vehicles.

The lifespan of green antifreeze is typically 36,000 miles or 3 years (whichever comes first). It shouldn't be mixed with other types of antifreeze fluids.

Orange antifreeze

Orange antifreeze, or OAT (Organic Acid Technology) is more suitable for newer vehicles, with engine designs that use more aluminium and plastic/nylon components than those built before 2000.

Unlike green antifreeze, it lasts longer and doesn't need to be changed as frequently. Its lifespan is typically 150,000 miles or 5 years (whichever comes first).

It shouldn't be mixed with other antifreeze fluids.

Red antifreeze

Red antifreeze is typically made with hybrid organic acid and lasts longer than green antifreeze, requiring fewer changes.

It should be replaced every 150,000 miles or 5 years, whichever comes first.

Which colour antifreeze should I use in my car?

It's important that you use the correct antifreeze in your vehicle, as the incorrect fluid may cause significant damage to the engine of your car.

The owner's manual for your vehicle will instruct you which colour antifreeze is best. If you are unsure, speak with a mobile mechanic.

Emergency antifreeze alternatives

If you run out of antifreeze it may be possible to use an emergency alternative until you can reach a garage or purchase replacement fluid.

However, before using any alternative to antifreeze, we would urge you to seek advice from a professional mechanic. Using an incorrect fluid or handling chemicals can cause serious harm to your health and your vehicle.

Water

If you have run out of antifreeze, water may be suitable as a short-term, temporary replacement.

However, it's important to note that water will increase the risk of the fluid freezing in the engine, as it has a much higher freezing point than antifreeze.

Homemade antifreeze

'Homemade antifreeze' usually refers to a mixture of water and ethylene glycol (the chemicals used to make green antifreeze).

It is not recommended to make your own antifreeze. The chemicals are dangerous and can cause serious harm to anyone who comes into contact with them.

Using the wrong fluids may also damage your car's engine and lead to expensive repairs.

Where to put antifreeze in your vehicle

To add antifreeze to your vehicle, locate the radiator or coolant reservoir, usually marked with a symbol of a radiator cap.

Remember that it is important to ensure the engine is cool before opening the cap.

You’ll then need to pour the antifreeze mixture into the reservoir or radiator until it reaches the recommended level.

Be sure to use the right type of antifreeze for your vehicle and avoid overfilling, as it can cause leaks or engine damage.