Will using the wrong coolant cause engine damage?
Updated 11 Oct 2019
Engine coolant is something you don’t think much about until the engine overheats or that warning light activates on the dash. When that does happen, and you are knowledgeable enough to check to see the coolant bottle is empty, the decision then becomes what type of coolant to use to refill the system.
Coolant comes in a selection of fruity-looking colours with various ingredients, and no one could blame you for standing in front of the coolant stand shaking your head and wondering which one to pick.
It’s actually pretty important that you pick the right coolant for your car. If you decide to just grab the sweetest-coloured coolant, slop it into the coolant tank and then tear off up the street without another thought, you could have some issues down the (not very long) track.
What is engine coolant?
Coolant is a water-based solution that includes inhibitors to protect the engine against corrosion and damage. Basically, and as its name suggests, coolant works to cool down the engine.
With all its moving parts, an engine generates a lot of friction and heat and the coolant passes through channels in the engine to withdraw that heat. It then flows to the radiator where it itself is cooled before heading back to the engine to start the process again.
Coolant also inhibits corrosion and scale build-up inside the engine and throughout the other components through which it moves. Water-cooled engines can rust over time and the coolant inhibits this process.
Engines are made of different materials - such as aluminium alloy, cast iron and other metals - and the coolant used in a particular engine needs to function well with those materials. This is why different coolants are available. One coolant is not best for all.
COOLANT What else is there to know?
Types of coolant
In Australia, there are two types of coolant - A and B.
: includes anti-freeze/anti-boil substances to raise the boiling point and lower the freezing point. Type A will usually have a Glycol base. The anti-freeze/anti-boil won’t break down over time but the inhibitors do, which is why the coolant needs to be replaced periodically.
: only contain corrosive inhibitors. There are different inhibitors in the various type B coolants and they are not necessarily compatible with one another.
Inhibitors provide a layer of protection for the metal or alloy engine components. When these break down, it raises the likelihood of engine corrosion. The lifespan of coolant is determined by the exhaustion of the inhibitors included within it.
Types of corrosion inhibitor:
: typically use silicates and/or phosphates
Organic acid technology (OAT) coolant
: this is an extended-life coolant. Corrosion inhibitors in OAT coolants act slower but last much longer than those in traditional coolants. It does not contain silicates or phosphates.
Hybrid organic acid technology (HOAT)
: usually a mix between OAT and silicates or phosphates.
Can you use different coolants?
The type of coolant and inhibitors to be used in a vehicle are determined by the vehicle’s manufacturer. This decision comes through the consideration not only of the type of vehicle, but the climate and region where the vehicle is to be driven. The same make and model of vehicle may use different coolant in Canada to one driven in Australia.
Mixing or using a coolant that is not recommended for a vehicle can lead to corrosion and damage not just to the engine but to components such as the water pump, radiator hoses and cylinder head gasket.
The colour of the coolant is not a reliable indicator of compatibility. Always read the packaging to confirm if the coolant is correct as per the manufacturer's recommendations. If you do mix different-coloured coolants they generally do not mix well and some can form a gel-like substance. This will halt coolant flow, causing blockages that can lead the engine to overheat, as well as damage to the radiator, water jackets and heater core. Also, the water pump can overheat and fail.
So, if you’re wondering if you can mix the red and green coolant to try and make a delightful yellow concoction the answer is a resounding NO! Don’t do it. If you do, the engine probably won’t explode immediately but mixing or using the wrong coolant is likely to cause engine damage and possible engine failure over time.
Booking with an AutoGuru professional mechanic to inspect and replace your coolant can save you from making any coolant blunders.
Rachel spent her early adult life around cars, motorsport and hands-on with her own cars. This interest moved into various careers within the Automotive industry. Joined with her passion for writing, Rachel loves putting the two together to share her experience, so we can all become AutoGuru’s.