Along with oil, coolant is a vital fluid for an engine. It’s worth checking the coolant in your engine regularly and if it needs topping up, getting the right coolant is important.

Look in your user manual

Your vehicle manufacturer will have specified a coolant for your car. You will usually be able to find this in the car’s user manual. Putting in the wrong type could damage your engine so it’s important to put the right coolant in.

Alternatively, go to a motor retailer but make sure you know the make, model and year of the car you want anti-freeze for.

What is coolant

Coolant is a mixture of water and antifreeze. It’s circulated round the engine’s cooling system by the water pump. It takes heat out of the engine and ensures components beneath the bonnet don’t get too hot.

There are different types of coolant

The anti-freeze component of coolant is designed to slow down or ideally prevent corrosion within the engine’s waterways. One of its primary purposes is hinted at by its name. It lowers the freezing point of the liquid in the engine so that the fluid doesn’t turn to ice when temperatures fall. If this were to happen, it could cause irreparable damage to the engine.

But it also raises the water’s boiling point which helps to prevent the engine overheating on long journeys in hot weather.

How do you know what they are?

The key is in the colour. Anti-freezes are coloured with different dyes depending on which type of corrosion inhibitor they have. This is what they are:

Green: Inorganic Additive Technology (IAT) – silicates

Orange: Organic Acid Technology (OAT) – Organic acids

Turquoise: Hybrid OAT (HOAT), phosphate free – NAP free

Yellow: Hybrid OAT (HOAT) – silicates and organic acids

Purple: Silicated HOAT (Si-OAT) – silicates and organic acids

Blue or pink: Phosphated HOAT (P-HOAT) – phosphates and organic acids

But what does it mean?

All those HOATs and OATs can appear pretty daunting. Loosely speaking, cars built after 1998 require silicate-free organic acid technology (OAT) coolant. Those made before 1998 need silicates in their anti-freeze.

Try coolant maker websites

Just as you can put your car registration into some websites and they’ll tell you which tyres you need, so you can do the same for coolant. Total, which provides coolants, has just such a service. You can access it by following this link.

Can you mix coolants?

If it’s an emergency, yes. But over the long term, it’s not ideal. The coolant won’t function as efficiently because you’re effectively diluting both different types.

Check the type of coolant

Some coolants come pre-mixed, others are sold as a concentrate. You need to dilute the latter with water. If you do this, make sure you do it to the correct ratio suggested on the coolant packaging.

Can you just use water?

In an emergency, yes you can. But it’s not ideal because of the properties of anti-freeze that we’ve outlined above.