Pouring coolant into a car

How much coolant does my car need?

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.

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What does coolant do?

Coolant is used to regulate engine temperature and helps to prevent two common engine faults:

  • Overheating, which occurs when heat is generated but can’t escape the engine compartment efficiently.
  • Freezing, which happens when ice forms within your vehicle’s radiator, blocking the circulation of water throughout the system.

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.

How much coolant is needed in a car?

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.

Does the amount depend on the car?

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.

How often do I need to top up the coolant in my car?

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.

What happens if I put too much coolant in my car?

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.

What type of coolant do I need?

There are three main types of engine coolant available:

  • Organic Acid Technology (OAT).
  • Inorganic Acid Formula (IAT).
  • Hybrid Organic Acid Technology (HOAT).

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.

How do I check my engine coolant?

  • Make sure the engine is cool. A good rule of thumb is to make sure the engine has been switched off for at least 30 minutes (or longer if you suspect it has overheated).
  • Locate the coolant tank. This is always under the hood of your vehicle and is generally connected to the radiator.
  • Inspect the coolant level against the ‘min’ and ‘max’ volume indicators on the tank. (A healthy coolant level should be somewhere between the two.)
  • Top up your coolant as needed (after double-checking that you are using the correct coolant type).
  • Use this opportunity to check for leaks or issues with the connected hoses.
  • If you have concerns about an unexpected drop in coolant level, the engine overheating/freezing - or issues with the coolant tank itself, take your car to a local garage.

What’s the difference between antifreeze and coolant?

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.

Can you put water in coolant?

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.