Last updated November 16th, 2023
Engine coolant plays a crucial role in regulating your car’s engine temperature. If you allow your engine’s coolant levels to run low, there is a much greater risk that it will overheat (or freeze).
When an engine overheats, the aluminium material will warp, swell - and sometimes, crack. This can cause lasting damage, leaving your vehicle in need of expensive repairs – or in the worst case scenario, a new engine.
If you intend to sell your car (or at least keep it running reliably for the foreseeable future), make sure that you maintain an optimal engine coolant level at all times.
In this guide, we will explain what engine coolant does, how much you’ll need – and how often you should top it up. We’ll also cover the various types of coolant on the market and how to check your engine’s coolant levels.
Coolant is used to regulate engine temperature and helps to prevent two common engine faults:
When used properly, coolant keeps your engine at an appropriate temperature, allowing air to circulate and preventing overheating or freezing.
Overheating or freezing can significantly damage your vehicle, so keep the engine topped up with the right amount of coolant at all times.
The average car’s cooling system holds about 5 litres of coolant – and most vehicles require between 3 and 7 litres of coolant at a time.
The amount of coolant you’ll need will depend on a variety of factors such as the car’s engine size, make and model.
If you are unsure how much coolant your vehicle needs, check the owner’s manual (or the manufacturer’s website) to avoid under or overfilling the cooling system.
There’s no universal answer here, but most cars need the coolant changing once every three years (or 30,000 miles). However, if you regularly make long journeys or drive in hot weather, you should change it more often.
If you overfill your car’s cooling system, the excess coolant could cause electrical damage to the vehicle. Therefore, you should pay close attention whilst filling to avoid going over the maximum fill level.
There are three main types of engine coolant available:
It’s important to ensure you use the correct type of engine coolant for your vehicle. An incompatible coolant could lead to a severe chemical reaction when mixed with the residue of a different coolant type.
Although the two are similar, antifreeze is a highly concentrated, glycol-based product which needs to be diluted with water before you can use it. Coolant is essentially a pre-mixed version of this product that is easier (and often safer) to use.
You shouldn’t add water to pre-mixed coolant. Pre-mixed coolant is generally already 50% water (which is the optimal concentration). Diluting it further could render the coolant ineffective.