Antifreeze FAQS

Common questions about antifreeze and coolant

Antifreeze is a clever liquid that plays an important role in keeping your car's engine in good health. But for it to work as it should, you need to use the right kind in the right concentration.

Here's our go-to guide for all your questions on antifreeze.

Engine coolant

What's antifreeze?

Antifreeze is a liquid that's added to a car's engine cooling system. It stops the water from freezing under normal cold weather conditions.

As well as lowering the freezing point, it also raises the boiling point of engine coolant. Along with a pressurised system, this helps to reduce the risk of overheating.

What's the difference between coolant and antifreeze?

Antifreeze is a concentrated product, normally based on glycol and containing inhibitors. Some types have to be diluted with water at a suitable concentration before you use it. The diluted liquid is usually called coolant.

Why do I need antifreeze?

Modern car cooling systems are smaller, with higher operating temperatures and pressures than in the past. That means it's especially important to use the correct additive.

If you don't use antifreeze, you could suffer serious damage to your car's radiator and other components if the water freezes or overheats. Water expands as it freezes which can spilt radiators or even break engine cases.

This vital liquid helps your engine in other ways too. It prevents scale building up and protects against corrosion, helping to keep your car healthy.

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What type of coolant should my car use?

The correct type of coolant for your car should be shown clearly in the vehicle handbook along with advice on recommended concentrations.

Without a handbook to refer to, you should check with a dealer.

How do I find out what type of coolant's in my car?

If you don't know what type of coolant's in your vehicle, it's not easy to identify it without sophisticated tests. The colour of the coolant isn't proof of the type or quality of product that was used.

If you're worried you've used the wrong type of coolant, it's best to take it to a professional mechanic who'll drain and flush the system. Antifreeze is a hazardous substance, so you should never attempt this yourself. Once it's empty, it can be refilled with the recommended type of coolant at the correct dilution level.

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How do I check my antifreeze strength?

The strength of your antifreeze can be measured using a hydrometer or a refractometer. Hydrometers are easier to use but can be less accurate.

Most garages should have these tools and be able to check for you.

I want to replace or top-up the coolant. What should I use?

For replacing or topping-up antifreeze, you should use the product recommended by the vehicle manufacturer or one that meets the specification set by them.

It is important when using concentrate to make sure that it's diluted to the correct mix with good quality water. You also need to wait until the engine is cold before topping up.

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Does sludge form when different types of coolant are mixed?

Good quality coolants shouldn't form sludge even when different types are mixed. Problems with sludge tend to happen with poorer-quality coolants or the use of very hard water (or both).

However, you should avoid mixing different types of coolant as it could make the corrosion inhibitors less effective.

The stuff the handbook says I should use is too expensive – can I use something cheaper?

For most people, a car is a big investment. In comparison, the price of even the most expensive antifreeze or coolant is relatively minor. Purchasing a good quality antifreeze or coolant will help to protect that investment.

Using a cheaper, inferior product could result in expensive damage to the cooling system or the engine and prove to be a false economy in the long run.

I care about my car – can I use a premium coolant or antifreeze instead?

While the vehicle is in warranty, you should use only the vehicle manufacturers' recommended fluids.

When out of warranty, use an antifreeze or coolant that meets the same specification and renew at the recommended times.

Who uses propylene glycol?

Propylene glycol (PG) based antifreeze or coolant is offered by a number of suppliers as a less-toxic alternative to ethylene glycol based products.

Good quality PG products perform very similarly to ethylene glycol based products. They're used by people who are worried about the toxicity of ethylene glycol based products.

No major vehicle manufacturers currently use PG based products for original fill. But PG based products are more widely used in Austria and Switzerland where there is legislation that restricts retail sales of hazardous products.

Do some vehicle manufacturers still use a high silicate antifreeze or coolant?

Currently, no vehicle manufacturers use high silicate products. For today's technologies, silicates are just one of many potential corrosion inhibitors.

If you do ever have a breakdown caused by your car's radiator, our parts and garage cover could save you money on repairs.

Published: 7 August 2019 | Updated: 16 October 2019 | Author: The AA

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