Can I Mix Engine Coolant or Top it Up With Water?

Even the most experienced of drivers sometimes wonders what they can and can’t do with their engine coolant. So, this post is an essential introduction to engine coolant – what it is, what it does, and whether or not you can mix it or top it up with water.

What is Engine Coolant?

Engine coolant is a mixture of water and anti-freeze. It does exactly what its name suggests, it keeps your engine cool and prevents it from overheating.

Do You Have to Top Up Engine Coolant?

The good news is that the majority of modern cars have sealed cooling systems. This means that you shouldn’t ever have to top up your engine coolant yourself. Trained professionals should take care of the process for you as part of your regular car servicing.

However, it’s still important to check your coolant, to ensure there are no leaks in your system that could lead to trouble.

How To Check Your Engine Coolant

You can check your engine coolant levels yourself. First, find your car’s expansion tank – check your manual if you can’t locate it. There should be min and max marks on the side of the expansion tank. Checking your levels is simply a case of ensuring your coolant’s somewhere between these two marks.

It’s good practice to check your coolant levels every couple of weeks, so you can address any problems as early as possible. Yet if there are ever any issues with your coolant, your car should tell you about it with a warning light on the dashboard.

Read our full guide to what engine coolant to use and how to top up.

Can You Mix Engine Coolant?

No, you should not mix two different types of engine coolant.

All engine coolants will involve a careful and precise mixture of water and anti-freeze. If you mix engine coolant, you could upset the proportions, ending up with too much, or too little, of either water, anti-freeze, or both.

Without the right mix, the engine coolant might not work as effectively as it should. Or worse, it could react badly with your engine, causing it to overheat, or to degrade.

Can I Top Up Engine Coolant With Water?

Although engine coolant is a mix of anti-freeze and water, it is not composed of ‘tap’ water. It uses distilled, deionised, or softened water – that is, water that’s had all of its essential minerals removed.

If you add tap water to your engine coolant, the minerals in the water can build up inside your car’s radiator. This can cause the engine to overheat, and in the long-term, it can lead to engine corrosion.

Even if you have the right sort of water, it might not be a good idea to top up your engine coolant yourself. You may not be able to get the right balance of water and antifreeze, so your cooling system may not be as effective as it should be.

Can I Use Water Instead of Engine Coolant?

No, water alone will not cool your system, even if it’s distilled or deionised water. If you just use water in your coolant system, it will expand as your car’s engine gets hotter. This can cause severe damage to your engine and radiator. Plus, water will freeze at lower temperatures, which again will result in seriously costly engine failure.

What To Do If You’re Worried About Your Engine Coolant

If you’re worried about your engine coolant levels, it’s best to head to a garage. Trained professionals can ensure your car’s topped up with the right stuff, while also checking for any leaks or other issues with your system.

Engine coolant failures are a highly common cause of breakdowns. This is why it’s vital that you check your system as often as possible.

For total peace of mind, consider taking out RAC breakdown cover as an optional extra available with your comprehensive car insurance. That way, if you ever do breakdown, at least you won’t be stranded.

At Go Girl, we offer new driver insurance that will give you all the cover you need at a price you can afford. Get a quote and instant cover online in minutes.