The radiator in your car is an essential, but often overlooked, component that is critical for optimal engine performance. Sitting at the heart of the cooling system the radiator ensures that your car stays cool as it heats up and that it can heat up if it starts off cold. But like every heart, the radiator needs blood, something which carries the heat around the system for dissipation or for accumulating it in the engine on cold days.

Coolant is the blood that flows through the heart of the radiator. Without it, the radiator cannot function properly, and neither can your car.

So today’s blog is going to take a closer look at how important coolant is in maintaining your car’s radiator, and how this contributes to increased engine performance.

What is Coolant?

Coolant is a fluid that helps to regulate the temperature in the engine by absorbing heat and carrying it through the radiator. Once in the radiator, the coolant is exposed to the air, which takes away as much of that heat as possible, before the coolant circulates back into the engine to pull away more heat and dissipate it through the radiator.

It is a mixture of water and ethylene glycol, the chemical component that both absorbs heat and prevents freezing. It is coolant’s ability to stay fluid down to -35⁰C or more that gives it the nickname ‘antifreeze.’ There are a few additives too which help prevent corrosion inside the engine and help lubricate the water pump.

There are 3 main types of coolant available on the market:

Organic Acid Technology (OAT): these are typically longer lasting and have additives which provide extended protection for the engine against corrosion and wear. Used in newer vehicles and often orange in colour.

Inorganic Acid Technology (IAT): Older and more traditional formulation, requires replacement more often and is usually found in older vehicles. Most commonly green in colour.

Hybrid Organic Acid Technology (HOAT): A combination of OAT and IAT, designed to give the benefits of OAT but be compatible with cars that take IAT coolant. Typically, yellow or gold in colour.

Importance of Coolant In Car Radiator Functionality

As the beating heart that is the radiator pumps coolant through the engine, it gathers the heat generated by the engine’s combustion processes and dissipates that heat by exposing it to air in the radiator itself. The coolant then travels back into the engine at a much lower temperature, ready to pick up more heat to dissipate.

On cold days, coolant is forced to stay in the engine, circulating as it heats, transferring heat to the metal quicker, and ensuring that even on cold days your engine can start and get up to optimal temperature quickly.

Coolant, therefore, allows the engine to both cool down when it is too hot, and heat up when it is too cold.

Heating up when it is cold is essential in colder climates and winter months. Car engines don’t do very well at cold temperatures, in fact, it has been proven that the hotter an engine is the better it works. Unfortunately, our modern materials, which are cheap enough and common enough to use in the majority of engines, simply cannot tolerate high heat without breaking down in some way.

But to ensure that the car can get up to temperature, and the oils and fluids don’t freeze, coolant is circulated transferring heat as it goes so that the parts of the engine that might be stuck, or frozen, thaw and move without causing any damage or problems.

On the other side of things, coming back to our super-hot engine, if the steel or aluminium or any of the metal in the engine gets too hot, it expands. If this expansion gets too much then parts of the engine will seize together, unable to move past each other due to their expanded size. The engine will still try to turn over anyway, forcing the parts to move and causing catastrophic damage to the engine.

So until we have amazing new thermal technologies that keep metals cool and engines hot, coolant is absolutely essential in ensuring your engine stays cool enough to function, but hot enough to perform optimally.

Maintaining Coolant Levels for Optimal Engine Performance

Knowing this then, we need to check our coolant levels regularly. Check your coolant levels at least once a month and refill as needed. If you notice coolant draining quickly, or the tank emptying frequently, it could be indicative of a leak, big or small, and it is important to get this checked and sorted as soon as possible.

If you know it is simply because it is time to top up coolant levels, ensure that your engine is off, and has been off for a while before opening the cap on the radiator or expansion tanks.

Expansion tanks are often built into radiators, but some cars store them separately. The expansion tank is where the coolant goes when it gets extremely hot. As it heats it expands, much like metal does, which means less coolant can travel through the engine efficiently. To combat this the expansion tank has a valve that is usually activated at 15psi, to ensure that the expanded coolant can find its way back into the expansion tank.

If your engine is cool, this mechanism is not activated and your coolant returns to the engine to heat up some more before trying its way past the valve again.

Because of this, if you open your radiator or expansion tank with a hot engine, you are liable to be splashed with scalding hot liquid.

So be sensible, be cautious. It is best to check your coolant on a morning when the engine has been off for several hours.

It is also important we use the right coolant for our cars, to ensure that the additives and types don’t interfere with engine performance. Your car owner’s manual should tell you this, or your local garage or mechanic can tell you easily too.

Benefits of using the Right Coolant for Your Car

As we have highlighted already, the main benefit is that your engine doesn’t overheat and therefore doesn’t explode. This is truly the most important function of your coolant.

Secondly, it ensures the engine can warm itself up on cold days, meaning you can still get to work or do the school run, even in the depths of winter, oh joy!

Thirdly, however, using the right coolant in your car can actually improve engine performance. A hotter engine burns fuel more efficiently, and therefore accelerates and performs better. And when fuel is burnt more efficiently, it is combusted more completely which means fewer greenhouse gases are coming out of your exhaust too!

It also helps to protect the inside of your engine from corrosion such as rust, or general wear, by offering a form of lubrication too.

Take all this together and coolant can really help to keep your engine working at optimal levels and increase the overall lifespan of the vehicle itself.


Coolant then is the lifeblood of the radiator, if the radiator is the beating heart that keeps the engine rolling and functioning properly.

It plays a vital role in managing the temperature of the engine as well as keeping the car in generally good health.

By regularly checking our coolant levels and ensuring they are where they should be we can prevent overheating or sluggish performance and increase the overall performance and lifespan of the vehicle and engine.

Take care of your car’s cooling system, and your car will take care of you for many years and miles to come!