Can I use any coolant in my car?

Posted 1 May, 2025 John Pedler

You’re checking under the bonnet and notice the coolant level has dropped below the minimum line in the overflow bottle, so you decide to top it up. Is it okay to use any type of coolant?

The coolant circulating through your car’s cooling system is designed to keep the engine at the proper operating temperature, and provide corrosion protection.

Are all coolants the same?

Short answer – no! The most common coolants contain ethylene glycol or propylene glycol for temperature control, water, a dash of corrosion inhibitor, and other additives.

Among the variety of coolant types available, there are specialised products for aluminium engines, heavy-duty diesels and some modern Japanese and European cars. It’s the inhibitors and additives that may differ between products, and not all these chemicals are compatible if mixed.

Some combinations may create corrosive acids that can damage engine components and seals, while others can create a gelatinous substance that gums up the cooling system, leading to overheating and expensive repairs.

Colour codes

Coolants come in a kaleidoscope of colours, including green, red, pink, blue, yellow, orange and purple. In the past, a coolant’s colour indicated its ingredients and compatibility, but that’s no longer the case.

The colours are simply dyes manufacturers use to identify their various products, and each manufacturer may use different colour coding.

What to do?

• Only use coolants the carmaker or coolant manufacturer recommends for your vehicle, and don’t mix different types of coolant.
• Coolants come as a concentrate or pre-mixed, so read the instructions before using it in your car.
• If you need to top up coolant but you’re not sure what type is already in your vehicle, then use distilled (demineralised) water.
• If you notice your car is using a lot of coolant, you may need the cooling system tested for leaks.
• When replacing coolant, the cooling system should be completely drained and flushed.
• See your car owner’s manual for coolant replacement intervals.

Warnings: Ethylene glycol is highly toxic, so keep it away from children and animals. Never open the radiator cap when the engine’s hot – this could result in severe burns.

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