The ultimate guide to coolant and antifreeze
Antifreeze and coolant are key to the safe and effective operation of your vehicle, but have you ever wondered what these important fluids are, their types, how important they are to your engine and how to solve problems with them? Get all the answers in our ultimate guide to coolant and antifreeze.
What is antifreeze?
Antifreeze is a chemical additive that reduces the freezing points and increases the boiling points of water-based liquids.
What does antifreeze do for vehicles? Well, it helps to keep engine components free from freezing up and overheating, protecting the engine from damage, safeguarding performance in hot or freezing weather or at the temperature operating limit of the engine.
What is coolant?
Coolant is a mixture of antifreeze and water, the ratio of which varies from vehicle to vehicle. Coolant ensures that the water in your vehicle’s radiator system does not freeze in winter, or boil and evaporate in summer.
A 50:50 mix of antifreeze and water is the most common – this raises the boiling point of water to between 240°C and 270°C, and lowers the freezing point to around -37°C. It’s important to always use coolant in your car, not pure antifreeze, as antifreeze has a much higher freezing point of around -20°C.
Types of antifreeze and coolant
All coolants contain a mix of water, antifreeze agents (such as ethylene glycol or propylene glycol) and corrosion inhibitors, of which there are three types:
- Inorganic Additive Technology (IAT) – Conventional low-silicate coolants, some of which require the addition of supplemental coolant additives (SCAs) every 25,000 miles or so.
- Organic Acid Technology (OAT) – Nitrate-free coolants that provide between 600,000 miles or 12,000 engine hours of service without need for SCAs.
- Nitrated Organic Acid Technology (NOAT) – Extended-life coolants containing organic acids, nitrate or molybdenum. They require SCAs every 300,000 miles or 6,000 engine hours in order to reach their 600,000-mile or 12,000-hour service intervals.
- Hybrid Organic Acid Technology (HOAT) – Combining OAT and IAT inhibitors, these low-silicate, nitrated coolants require an SCA after 25,000 miles or so.
Can you put water in coolant?
If you are running low on coolant, you can top up the coolant reservoir with water, however this will reduce its boiling point and raise its freezing point, putting your engine at risk. As such, you should always replace the watered-down coolant with the mixture recommended by your manufacturer when you return home.
Common coolant problems
If your car is leaking coolant, there are several potential sources, including a defective water pump, radiator, hose, freeze plug, intake manifold gasket, heater core, head gasket, ATF oil cooler, cylinder head or cylinder block. Therefore, always visit a mechanic if your car is leaking antifreeze – often, they will pressure test the cooling system to find the leakage and repair accordingly.
Oil in coolant
Coolant and oil should never mix. If they do, the performance of either will be greatly diminished, potentially causing harm to the engine.
If you find oil in your coolant reservoir, there are a range of potential culprits, including damaged cylinder head gaskets, cylinder heads, engine block, the presence of too much water in the engine, or even excessive overheating. With so many potential sources of the issue, it’s best to always consult with your mechanic if you discover oil in your coolant.