Antifreeze - FAQs

Frequently asked questions about antifreeze and engine coolant

Antifreeze is a concentrated product, normally based on glycol and containing inhibitors

Antifreeze is a concentrated product, normally based on glycol and containing inhibitors.

It's important to make sure you use the right antifreeze at the right concentration.

Modern car cooling systems are smaller and operating temperatures and pressures are higher which makes it even more important to use the correct additive.

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.

What is the difference between coolant and antifreeze?

Antifreeze is a concentrated product, normally based on glycol and containing inhibitors. It has to be diluted at a suitable concentration for use. The diluted liquid is usually called coolant.

How do I find out what type of coolant should be in my car?

The correct coolant for a vehicle will be indicated in the vehicle handbook; if no handbook is available then ask at your dealership.

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

If the type of coolant in a vehicle is unknown it is not easy to identify it without the use of sophisticated analytical procedures. The colour of the coolant does not prove type or quality of the product. The best course of action is to drain and flush the system and refill it with the recommended type of coolant at the correct dilution level.

Who uses propylene glycol?

Propylene glycol (PG) based antifreeze/coolant is offered by a number of suppliers as a less toxic alternative to ethylene glycol based products. Good quality PG products have a very similar performance to ethylene glycol based products and they are 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.

What's a refractometer? And when do I use one instead of a hydrometer?

A refractometer is a device used to measure the refractive index of liquids. As there is a good correlation between the concentration of antifreeze in a coolant solution and the refractive index, a refractometer is used to determine the concentration of antifreeze. A refractometer is easier to read and more accurate than a hydrometer. As they are more expensive they are more usually used in workshops rather than by private motorists.

Which types form sludge when different types of coolant are mixed?

Good quality coolants should not form sludge even when different types are mixed, problems with sludge tend to be associated with poorer quality coolants and/or the use of excessively hard water. Mixing different types of coolant should be avoided as it could reduce the effectiveness of the corrosion inhibitors.

Are some vehicle manufacturers still using a high silicate antifreeze /coolant?

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

I want to replace/top-up the coolant, what should I use?

For replacing or topping-up, you should use the product recommended by the vehicle manufacturer or meeting the specification indicated by the vehicle manufacturer. It is important when using concentrate to ensure that this is diluted to the correct mix with good quality water.

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

For most people a car is a significant investment, in comparison the price of even the most expensive antifreeze/coolant is relatively minor. Purchasing a good quality antifreeze/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 one of the premium coolant or antifreezes instead? Would it be waste or could there be problems?

While the vehicle is in warranty you should use only the vehicle manufacturers' recommended fluids. When out of warranty, use an antifreeze/coolant meeting the same specification and renew at the recommended times.

(29 November 2011)