Coolant and antifreeze perform similar jobs and many will class them as one and the same. However, there are several key differences between the two.

You need to know these differences, as well as why they both work well together and why they're so important to your car. If you don't, you could cause yourself some expensive problems. Without coolant, your car will overheat and it could freeze in cold weather without antifreeze - and a new radiator isn't cheap!

By the end of this guide, you'll understand:

  • The differences between antifreeze and coolant
  • How to best utilise them
  • How to check your coolant
  • Problems with a low coolant level
  • And what to do if you need more coolant and antifreeze


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Is Coolant the Same as Antifreeze?

Coolant is a diluted form of antifreeze. This means they have the same base properties but work best in different climates. Coolant protects your radiator all year long and antifreeze is designed to give it some added protection in the winter. Good quality coolants tend to have antifreeze properties as standard, but it's always worth checking.

As a result, antifreeze and coolant are not interchangeable. You can use coolant without antifreeze, but you can't use antifreeze without coolant.

Here's another way to look at it. Let's imagine coolant as the centre-half pairing in a football team and your car's engine the goal they're defending. Now, that makes antifreeze the defensive midfielder. This player will sit deeper than the rest of the midfield and give an extra layer of protection to the defence.

Every team picks at least two centre-halves in their starting line up to give their goal a good level of protection, but a defensive midfielder is an optional tactical decision. The team will still function without them, but you give yourself a better chance of keeping a clean sheet if they play. The centre-halves and the defensive midfielder are tasked with stopping the ball from going in the goal. The difference is how they carry out that duty.

Both a defensive midfielder and antifreeze are an extra level of protection. Your car would still function without it, but it works even better when antifreeze helps coolant protect your engine from temperature-related damage.


Where Does Antifreeze Go?

You can add antifreeze straight into the coolant tank The two fluids are very compatible and mix together quickly, so there's no need to overcomplicate the process or look for a separate tank  


What Do the Different Colours Mean?

Coolant comes in various forms, which you can usually identify by the colour of the liquid. Here are the main three:


Bright Green - Inorganic Acid Technology (IAT). Often used in older cars and contains phosphates (corrosion inhibitors) and silicates.

Orange or Red - Organic Acid Technology (OAT). Found in most modern cars and provides high-temperature protection for aluminium. 

Orange or Yellow - Hybrid Organic Acid Technology (HOAT). A combination of IAT and OAT, HOAT coolant has an extended lifespan.


However, coolant can also come in pink, blue and several other colours. A lot of it depends on what type your car's manufacturer uses. Make sure you always keep the colour of coolant consistent as mixing the wrong types can cause radiator and cooling system damage. You should check your vehicle handbook or seek professional advice if you're unsure.


How To Add Antifreeze to Coolant

You must diluted antifreeze for the best results. Check whether yours is already pre-mixed and, if not, add de-ionized water in at least a 50/50 split before adding it to your coolant. Tap water is not recommended because it has too many minerals in it. From there, just pour it into the coolant tank. You should dilute your coolant in the same ratio if it has not come pre-diluted.

Adding antifreeze neat reduces its efficiency, so we would advise against doing so. When diluted, it cools your engine by transferring heat through a convection process. This reduces the strain on your radiator and your chances of overheating, allowing your car to run efficiently, no matter what the temperature. If you add antifreeze neat, the convection process doesn't work as well.


So, antifreeze is subtly different from coolant, and it's clear why this is. But you might be wondering why there is even a need for coolant and antifreeze in the first place. Surely it's only an added expense and water will work just as well?


Can You Put Water in a Coolant Tank Instead?

You should avoid using water instead of coolant as much as possible. There are many different opinions on the subject, but more experts advise against it. In fact, you can cause expensive engine damage if you regularly use water instead of coolant. Water freezes at 0°C and boils at 100°C - temperatures which a working car engine can exceed under normal driving conditions. Water doesn't work well outside these temperatures, so you will increase your radiator's chances of freezing or overheating, especially if you live in a cold climate. 

However, you can put water in the coolant tank in an absolute emergency, like if your car has overheated as a result of a leak. Even so, you will still have to deal with the leak and water will rush out as easily as coolant. That's why you're better off getting towed to a local garage to get the problem fixed quickly (more on this later).

We recommend using diluted coolant and antifreeze at all times for the best results.


As your coolant and antifreeze are so important, you must know how to spot a problem with them. While it's easy to spot a leak, how do you check your coolant for other issues?


How to Check Your Coolant Level

A coolant check is a simple process that you can do at home. We recommend checking this fluid regularly, just like you would with engine oil or your screenwash level.

Your coolant tank should look like this:

coolant reservoir  

Most tanks are transparent, so you can see the level easily. If it doesn't reach the 'full' line on the side, top it up with a mix of coolant, antifreeze and water until it does. You should only open the radiator cap if you can't see the level through the side or you need to look at something more closely (i.e the coolant is contaminated or you're concerned about a potential leak)

Be sure to wait for the engine to cool before checking the coolant. It boils while you drive along, and will release scalding hot steam out of the radiator cap. What's more, you will create a sudden change in temperature and pressure which can crack the engine block. Check your coolant before you switch your engine on or at least half an hour after you switch it off. 

If your coolant is brown, opaque or has bits floating in it, you need to book a coolant change immediately. It should be transparent at all times, no matter what colour it is. Contamination reduces its efficiency so, the longer you leave it, the greater your chance of an expensive repair bill. A professional coolant change is a cost-efficient way of avoiding this.

You should also book an appointment at a garage near you if your coolant level is low.


Problems With a Low Coolant Level

Your car doesn't consume coolant like petrol or engine oil. The level shouldn't drop much during normal use so, if you're constantly topping up or have to add a lot at once, there could be a leak.

Don't ignore it.

A leak increases your car's chances of overheating and causing damage to the water pump, head gasket, cylinder and piston timing. These are all expensive repairs that can set you back thousands of pounds. In contrast, the average coolant change cost in the UK is less than £100.


What to Do If You Need More Coolant and Antifreeze

You can buy bottles of antifreeze from local auto stores for £5 - £20, depending on how much you need.

However, if you notice a problem with your coolant, topping it up won't solve the issue. You need to drain your system and refill it with high-quality coolant and fix any leaks.

And for that, you need to book a coolant change at a garage near you. Enter your reg and postcode into our online comparison site to compare deals in your area and book with your ideal garage. You can sort by distance, availability, price or reviews - whatever matters most to you.

Most importantly, you shouldn't avoid a repair. Your car needs coolant to work properly all year long and avoid those expensive repair bills. If you have a leak or poor-quality coolant, your chances of a breakdown increase.





Coolant is a diluted form of antifreeze that protects your engine from overheating. Adding antifreeze on top offers an extra layer of protection in the winter. As a result, you can use coolant without antifreeze, but not the other way around. You can put antifreeze straight into the coolant tank but there may be a leak if you need to top up a lot. Check your tank regularly and book a coolant change if the fluid is brown or there are bits floating in it. Ignoring this is very bad news because it becomes less efficient. This increases the chances of your radiator overheating and causing expensive engine damage.