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Antifreeze verses Coolant. What’s the difference?

So what is the difference between Antifreeze and coolant? (Which to further confuse things is also known as summer coolant).

Your car has been out on the drive all night and the temperature has dropped to -9°C yet the car starts first thing in the morning, even if you don’t. Or maybe this summer you have driven to the Cotê D azure it has been a constant 35°C all day and yet you drive all day without the engine overheating.

Admittedly these are things that most drivers take for granted, after all this is just what cars are designed to do isn’t it?

Well yes and no, but in each of the above situations you can thank your engine coolant additive for this wide range of performance.

Antifreeze is a bright green or yellow chemical that is mixed with the water in your cars engine, radiators and cooling system, it is there to stop your engine from freezing or overheating.

The Technical bit

Antifreeze or coolant is a chemical, usually either Ethylene glycol or propylene glycol which, when added to the water in your engine changes the freezing point and the boiling point of the water. (there are other chemicals used as antifreeze, but we will stick with these two)

With the correct mix of chemical, which is often recommended as 50% water to 50% antifreeze (sometimes referred as 50/50) the water freezing point moves from 0°C to approximately -35°C.

Ok I hear you say, but why antifreeze in the heat of summer? Well, the boiling point of water is also affected by this mixture of chemical and water and increases from 100°C to just over 125°C at a normal engine system pressure of 15lb/in² this is sufficient, in a healthy engine, to stop the coolant from boiling. So, there you are, the same chemical will stop freezing and boiling, by how much will depend on the mixture levels dependant of the mixture levels. 50/50 being the recommended minimum but in some vehicles, it is quite normal to have waterless cooling so ask us if you are not sure.

There is another important characteristic of antifreeze or coolant additives. This is mainly associated with effects of corrosion and sludge creation in your engine waterways, pipes and radiators. Corrosion and sludge will occur if you are using only water as the coolant for your engine. Most modern antifreeze agents include other chemicals to improve heat transmission and reduce corrosion, the chemicals included will depend on the engine’s design and materials. Aluminium engines will require a different antifreeze from iron or steel blocks and engines using a cylinder liner.

That antifreeze doesn't just prevent freezing it is an important component to extend the life of your engine and ensure problem free motoring.

If you are in any doubt about the antifreeze/­coolant you need for your car just give our MotorNuts Technicians a call on 01254 778255 or use our free advice link on any page of the motornuts.co.uk web site and ask a MotorNut we will be happy to help selecting the right antifreeze for your car.

It is worth buying an antifreeze tester from about £12 to check the mixture levels.

We at MotorNuts stock an antifreeze to match the needs of all the modern major car, van, truck and motorcycle engines, including Castrol, Comma, Granville and Prestone antifreeze/­summer coolants as well as BlueCol specially formulated for classic and vintage vehicles.