All you need to know about coolant and antifreeze for your car


The colder the weather gets the more drivers should consider the coolant in their car. This is because engines need liquid circulating through them to keep cool. But freezing weather can turn that fluid to ice, rendering it useless.

Coolant is vital because when a car is going at speed, pistons travel at around 40mph, shafts whizz round and bearings are under extreme pressure causing heat to build up. To stop this becoming so intense that metal parts begin welding themselves together, coolant is used. Here’s all you need to know about it.

Is coolant the same as antifreeze?

The answer is both yes and no. Technically you could have a coolant with no antifreeze in it. How long the engine would last is debatable. Hence engine coolant tends to be antifreeze combined with water.

Antifreeze is ethylene glycol, or the less toxic propylene glycol. These chemicals are mixed with water because in very cold weather water would freeze. Equally if it gets very hot, water boils and turns to vapour. In either instance, it becomes useless for cooling and an engine that gets too hot can suffer damage. Anti-freeze both lowers the freezing point of water and raises its boiling point thereby guaranteeing the engine stays cool enough to perform efficiently and reliably.

What should I do if I get low coolant warning?


If the engine doesn’t have sufficient liquid to cool its components, it will get so hot that moving metal parts could start fusing. A red engine warning light will come on if there isn’t enough coolant. You should stop the car as soon as it’s safe to do so. Lift the bonnet and check the coolant level. Keep on driving and you could cause permanent harm to your engine.

How do I check my coolant level?

Look in your car’s user manual. It should show you where the coolant expansion tank is beneath the bonnet. This will be light-coloured plastic so you can see the level of the liquid it contains. On the outside it will have ‘min’ and ‘max’ markers. The liquid inside should be somewhere between these two points.

How do I put coolant in?

The tank will have a removable cap. Don’t remove this if the engine is hot. This tank is for expansion and designed to relieve excess pressure if the engine gets very hot. Removing the lid when the engine’s hot will release steam that could scold you. Let the engine cool down, then remove the cap and add coolant until it’s between the ‘min’ and ‘max’ points.

The amount of coolant that engines need varies from car to car. If there is no coolant left in the reservoir at all, there’s every chance you’ve got a leak. It’s pointless putting more coolant in because it’ll simply leak out again so ring your breakdown service.

What do I put in?

There are two types of coolant. Both are available online or from motor retailers. Coolant either comes ready mixed – usually half antifreeze, half water – or is concentrated antifreeze. If your coolant needs topping up and you use water on its own, you risk diluting the antifreeze. This may make it less effective in cold weather.

The manufacturer of your car will have a recommended coolant for the stresses and strains of your model’s engine. This should be specified in the user manual. Alternatively, on some retailers’ websites, you can enter your vehicle details and it’ll tell you what antifreeze you need.

How much antifreeze do you have?


If you buy a used car, it’s impossible to know precisely how well it’s been maintained. And that includes the cooling system contents. Garages can check the concentration of antifreeze within coolant and then adjust the balance to ensure it’s sufficiently strong to work in icy weather.

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