Can you mix different coolant colours?
12/30/2024 12:00 AM
There are a variety of coolant colours, but that might not be the only difference between them. We investigate whether it’s ever okay to mix them.
Coolant is imperative to keeping your car from overheating and stopping heat from causing significant engine damage.
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You should change your coolant at least once every two to three years to ensure that any contaminants are removed from the cooling system.
Perhaps you have just fixed a slight leak and need to top up your coolant. There are a plethora of different-coloured coolants to choose from. But can you mix two together? We investigate.
Can you mix different-coloured coolants?
Different-coloured coolants have other properties besides just the colouring used. Rolls-Royce/Bentley mechanic James Boer says you should always use the same coolant colour.
"Each coolant has different active ingredients, whether it be the anti-boil properties or anti-freeze in colder climates. They are made differently for manufacturers and climates. Mixing them can decrease their performance potential, leaving a lacklustre outcome," says Boer.
"Manufacturers design and build their engines, hoses, rubbers, and seals to work with certain coolants; premature failure can be caused by using the wrong coolant.
"If you need to top up your coolant and you can't find the same colour, it would be a better idea to slightly dilute your coolant with water instead of mixing it."
The main difference in coolants of varying colours is their base.
Green coolant
Green coolant is the most common and historic of all coolants. It has an ethylene glycol base and can be used in a wide variety of cars. It has great heat transfer properties and a very low freezing point when mixed 60/40 with water at -45°C.
Green coolant is suitable for most types of radiators and engine blocks, as well as aluminium or iron.
Red coolant
Red coolant, which can sometimes be pink, is the second most common application. It uses an organic acid base instead of ethylene glycol and does not contain silicates or phosphates.
Red coolant is used in some vehicles because the silicates and phosphates found in green coolant can damage certain types of seals, gaskets, and metals made from nylons and some alloys used in the engine construction of newer vehicles.
Red coolants also have a higher boiling point compared to green coolants, as well as longer life spans.
You should reference your owner's manual to ensure that your vehicle is compatible with red coolant.
Blue coolant
Blue coolant is another organic acid-base solution similar to red coolant, but it does not contain borate.
Again, borate in some newer vehicles can harm the seals and materials used to construct engine components. You should only use blue coolant when specified, as borate helps keep the pH at a certain level to avoid acid formation.
Yellow/orange coolant
Yellow and orange coolants use a hybrid organic acid technology, which combines an organic acid base with ethylene glycol-based coolants.
Yellow coolant is typically universal and can be used in almost all cars (provided the existing coolant has been flushed). It features the superior anti-freeze/anti-boil properties of organic acid-based coolants and the anti-corrosion silicates of an ethylene glycol-based coolant.
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