Antifreeze & Coolant: What, Why and How to Check

Car Coolant

It’s important that you know the difference between antifreeze and coolant, so we’ve created the ultimate guide. We’ve explained what they are, what roles they play, how they interact with each other, where you can buy them and how you can check, change and use bother fluids.

What is Antifreeze?

Antifreeze is a concentrated additive which, when mixed with coolant, helps protect your car’s radiator from freezing during the winter. It’s usually orange or green in colour. Orange antifreeze has an extended lifespan thanks to a different corrosion inhibitor used. However, either colour will work for you as they both do the same job.

Antifreeze is a cold-weather variant of coolant. It’s really that simple.

They’re not separate entities and they’re not interchangeable either. While you can use coolant without antifreeze, you can’t use antifreeze without coolant. This is because antifreeze only protects your engine in cold temperatures.

The sweet smell of antifreeze makes it appealing to small children and pets so, if you’ve opened a bottle of antifreeze, keep it out of reach with the lid firmly screwed on. It needs to be washed off of skin and paint immediately as it is classified as an irritant.

Usually, good quality coolants have antifreeze properties in them already, so you don’t always need to add it separately. But, if you do, we’ll explain how to later on.

So, What’s the Point in Having Both?

Let’s look at it another way.

When a football team is protecting a 1-0 lead with three minutes to go, they might bring on a defensive midfielder to try and shut up shop. That defensive midfielder adds a bit of extra protection in front of the two centre-halves already protecting the goalkeeper. The team keeps a clean sheet, records a 1-0 win and everyone goes home happy (apart from the opposition supporters).

On the flip side, a team wouldn’t start a match with a defensive midfielder but no centre-halves as there wouldn’t be enough protection for their goal, would there?

Now, if we imagine the centre-halves are coolant, the defensive midfielder is antifreeze and the goal is your engine, things start to make a lot more sense.

The two centre-halves stay on the pitch for the full ninety minutes, much like coolant offering all year around protection of your engine. The defensive midfielder is an optional tactical decision, just like adding antifreeze. Both are utilised at critical times to add another layer of protection. For your engine, it’s during the cold winter months; for a football team, it’s the last few minutes of a game.

Playing without centre-halves leaves you especially vulnerable to a heavy loss just like driving without coolant leaves you at risk of overheating your engine. And that just doesn’t make any sense at all.

It’s adding that extra protection which makes antifreeze so important and explains why most coolants already come with antifreeze additives. This is equivalent to a balanced midfield which offers options in both defence and attack in our football analogy.

Makes a lot more sense now, right?

Antifreeze bottles

Where Can I Buy Antifreeze and Coolant?

Now you see the benefits, naturally you want to buy some. While it’s not as easy as popping down to the local supermarket to buy a bottle, coolant and antifreeze are widely available from most automotive retailers. Either search online or drive to your nearest store and pick up a bottle.

However, as with everything, it’s worth making sure you’re using the correct type. Your vehicle’s handbook will tell you the correct coolant your car needs. Never use one that doesn’t meet this specification as you could damage your engine. If you’re ever in any doubt, ask a professional mechanic!

How Do I Use Them?

For best results, use a 50/50 or 70/30 antifreeze/water split when adding to the coolant. Never add antifreeze neat as the corrosive high concentration level won’t do your engine any favours.

Always dilute coolant as well. A 50/50 split works best, whether you’re adding antifreeze or not.

Speaking of doing your engine a favour, there are few things you should never use as a substitute for coolant. Screenwash may have similar properties to antifreeze, but it doesn’t mix well with coolant. While it stops the glass from freezing when used on your windscreen, it doesn’t do a great job of protecting a radiator, unfortunately.

It’s also not recommended to use water as a replacement for coolant either. It will do the job in an emergency, (i.e. you’ve run out of coolant and you need to drive somewhere to buy some), but it won’t protect you from overheating in the long run. If you do have to use water, make sure to fill up with coolant as soon as possible and get a mechanic to check that you haven’t damaged your engine at all.

Avoid consequences like this by checking your coolant levels regularly.

How to Check Your Coolant and Antifreeze Levels

Thankfully, it’s simple to do: just open your bonnet and look for the coolant reservoir. As with anything under the bonnet, consult your vehicle’s handbook if you’re not sure. All the answers are in there.

When it comes to checking and topping up the coolant reservoir, we’ve got three top tips:

  • Don’t immediately open the radiator cap
  • Wait for the engine to cool before checking the coolant
  • Don’t go looking for a separate antifreeze reservoir

You can check and top up coolant quite easily. However, if you notice that your coolant is brown or there’s bits floating in the coolant, it needs draining immediately. Contamination isn’t brilliant for your engine and the flush can only be completed by a professional mechanic.

coolant reservoir

Don’t immediately open the radiator cap

Most coolant reservoirs are transparent, so you can see the level without much difficulty. You should be able to see whether it reaches the full mark on the side. If it doesn’t, top it up with a mix of coolant and water until it does!

Only open the radiator cap if you can’t clearly see the level through the side or you need to look at something more closely – (i.e. you suspect the coolant has been contaminated).

Wait for the engine to cool before checking the coolant

Vehicle maintenance always needs to be done when the engine is cool.

It’s not a good idea to check your coolant while the engine is still warm. You could scald yourself as the boiling coolant releases steam out of the cap or you could crack the engine block.

The sudden change of temperature and pressure won’t do your engine any favours. Rather than risk an expensive repair, wait half an hour after your journey before checking your coolant. Alternatively, you could do it before you leave.

Don’t go looking for a separate antifreeze reservoir

That’s right, antifreeze goes straight in the coolant reservoir.

The two fluids mix together anyway, so your car just makes your job easier for you. Make sure you dilute the antifreeze with water before adding it and don’t go overfilling the reservoir either. If you notice your coolant level has dropped, consider adding antifreeze to top it up. You stand a much better chance of running perfectly all year round that way.

Here’s What to Do if You Ever Notice Any Problems

Your coolant level should remain more or less the same no matter how much you drive your vehicle. It’s not like oil which burns away during use – so, if it looks like it’s draining fast or you’re constantly topping up, there could be a leak somewhere in the system.

Don’t ignore it.

Coolant is vital to the function of your car, so book an appointment with a mechanic as soon as possible. You don’t want an overheating engine – or worse!

Contamination is a significant issue as well. If you notice the symptoms we’ve mentioned above, your system needs to be drained and re-filled. The same goes if you’ve used the wrong kind of coolant or haven’t diluted it properly.

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Hopefully, you’re now a bit more clued up on coolant and antifreeze. We’ve covered what they are, what they do and how you can check them. But there’s one final question to ask:

When was the last time you checked your coolant?

If you can’t remember, or you think it was a long time ago, perhaps now’s the right time.

Was this guide helpful? Perhaps you’ve got more coolant or antifreeze related questions you’d like answering? Whatever they may be, just drop us a comment! We’re here to help you after all.

Mandy Weston

Mandy Weston

Mandy is an ex-mechanic, with 22 years’ experience in the motor industry. As an in-house motoring expert, Mandy is the go-to woman for any relevant questions that our customers have; both garages and drivers. From specific problems with your car to general maintenance, Mandy is a reliable source of information and advice. Her passion for motoring is a huge factor to her success and the huge wealth of knowledge that she has. She now uses her remarkable grasp of the industry to write regular content for our readers to help drivers understand their car better, avoid being ripped off by garages and save money on their motoring requirements.