Skip Content
Sign in to the member area
Coronavirus Update + Support >

What is antifreeze or coolant and how can you check your car’s fit for winter?

As the winter weather sets in and sends a chill down your spine, spare a thought for your car’s engine.

James Mills
Written by James Mills
Edited on
Main image

It relies on a cooling system filled with special fluid to keep the engine cooled when its running or even switched off but without the right mix of fluids the motor could be seriously damaged by the effects of freezing temperatures. So what should you do to keep everything running smoothly? Here’s everything you need to know to stay safe in the winter.


What is engine antifreeze and coolant?

Antifreeze and coolant are an engine’s lifeblood. Coolant is distilled water mixed with antifreeze. Together, they circulate around cavities within the main part of the engine to keep the temperature at its optimum operating point, before being passed through a radiator, which uses airflow to cool the fluid.


Why does coolant need to be mixed with antifreeze correctly?

The job of antifreeze is to stop the coolant freezing. It also prevents corrosion, and when stored within a pressurised system the boiling point of the cooling system is raised.

If it isn’t used or mixed correctly, the cooling system won’t work effectively. And in freezing temperatures, there is a danger that the fluid of the coolant system will freeze, meaning it will expand and cause serious – and expensive - damage to parts of the engine.


Routine servicing cares for your car’s coolant

The mixture of antifreeze in coolant is prescribed by the vehicle manufacturer. By following the servicing schedule for your car, any reputable garage will always check the concentration of a car’s coolant. They will also drain, flush and replace it according to intervals set by the car maker, then pressurise the system.


How to check an engine’s coolant level

It’s important that drivers check the level of their car’s coolant system and ensure that it is full. Because if it isn’t, there could be a leak in the system.

The vehicle handbook will detail where to find the expansion tank in the engine bay. Park the car on level ground, switch off the engine, ensure the handbrake is applied then open the bonnet.

There will be a plastic chamber, known as an expansion tank, which will be marked with minimum and maximum points, and the level of coolant visible should sit between these.


What to do if an engine’s coolant level is low

If the coolant level is visibly low, or a warning light is showing on the car’s dashboard, don’t panic. When the fluid is hovering around or just below the minimum mark on the plastic tank in the engine bay, it should be alright to drive the car to a garage and have it checked. Alternatively, if you are concerned it’s too low, call out a breakdown service.

Unless you are skilled at car maintenance, don’t attempt to top up the coolant system yourself. It is pressurised, and before work starts it should be inspected for leaks. Once drained, it should also be flushed to ensure it is clean before fresh coolant, mixed with the correct concentration of antifreeze, is added.

Thinking about switching to all-season or winter tyres? Unsure of the differences? Find out everything you need to know, here.