Checking up on your engine coolant is easy to forget, but an engine’s coolant is just as important as oil when it comes to your car. Coolant does raise the boiling point of the cooling system fluid in summer, lowers the freezing point in winter, and protects the engine and cooling system from corrosion. These functions keep the engine from overheating or freezing when driving in extreme climates.
Engine coolant needs changing because chemicals in the fluid break down and become less effective over time. This use ends up generating rust and sludge, which can damage the cooling system. If the cooling system becomes damaged, you risk the possibility of the engine overheating–a much costlier mistake than paying for a coolant flush.
What is Engine Coolant?
The gasoline or diesel engine in your car or truck produces the necessary power to push you down the road. At the same time, that engine produces a considerable amount of waste energy in the form of heat. And that heat must be extracted from the mechanisms inside the engine and efficiently dumped to the outside air.
How does this happen? Well, unless you are driving either an old VW Bug, a Chevrolet Corvair, or a Porsche, your car will have a “water” cooled engine. Your car will also have an engine with internal water passages, a water pump, a heat exchanger called a radiator, and a bunch of flexible hoses connecting these things together.
How does all this work? When the engine is running the water pump circulates the cooling water through the engine and out to the radiator. The hoses convey this fluid.
Every time you drive, the water picks up heat from the engine and releases that heat into the air flowing through the radiator. This prevents your engine from overheating.
In the description above, “water” is the term used for the cooling fluid. But the cooling fluid will not be just water but a blend of water and antifreeze. The technical term for this blend is coolant.
Simply put, engine coolant is the liquid that functions to cool the engine in your car. To fully understand the automotive coolants of today, we must first look at the qualities of the pure water once used for this purpose.
For cooling engines, water has some very positive qualities.
- It has a very high specific heat value. That is, water can hold more heat per unit volume than almost any other fluid.
- It has a reasonably high boiling temperature.
- It is available virtually everywhere at a remarkably low cost.
There is no question that these three factors made water the coolant of choice in the early 1900’s when engine-driven vehicles came on the scene. But there are several problems with using water alone that made it then and even now less than the ultimate engine coolant.
- Water has a freezing temperature of 32 degrees Fahrenheit which makes it unsuitable for engines used in most high latitude climates worldwide.
- Worse yet, when it freezes, it expands. This behavior can crack any engine cooled in winter with water alone. And it can also freeze inside a radiator and easily destroy that costly part.
- Water encourages corrosion (creates metal oxides or rust) with the materials commonly used in engines and radiators.
Very early in the development of engines, chemists began to modify water with added chemicals to make it a more suitable coolant. These additives focused both on overcoming water’s disadvantages discussed above while still retaining the positives that water brings to keeping things cool.
Different Types and Colors of Engine Coolants
When it comes time to top off or do a complete system flush, you are going to have to find the right coolant for the job. It would be convenient if every manufacturer used the same coolant, but they do not. There are three main types of coolant that car companies use: Inorganic Additive Technology (IAT), Organic Acid Technology (OAT), and Hybrid Organic Acid Technology (HOAT).
The truth is color is not a reliable predictor for what type of coolant you have. For example, OAT coolants are usually orange, yellow, red, or purple. HOAT coolants are orange and yellow for the most part. Then the older IAT coolant is green. Coolants that manufacturers sell can confuse matters even more, like Honda’s blue coolant.
That is why you need to read what the bottle says and not rely specific color you are pouring. If the bottle’s description has you tripped up, check your owner’s manual for the right kind of coolant.
Finding the Right Fluid
Typically, older cars use IAT. It needs to be changed every two years or 24,000 miles, making it far inferior to newer formulas. One of those newer formulas is OAT. General Motors vehicles use this formula and normally require a change after five years or 50,000 miles. Finally, HOAT is a derivation of OAT that requires the same time change interval unless otherwise specified.
The easiest way to make sure you are getting the right coolant for the job is to go to your car’s dealership. They will sell the coolant for your specific make and model, and it is guaranteed to be the correct one. Many times, the coolant is branded for the car you are going to put it in.
For example, Honda sells its Type 2 Antifreeze/Coolant in all its dealers. Plenty of others like BMW and Volkswagen do the same thing.
Not every manufacturer does this though. All GM cars use something called Dex-Cool from the factory. Ford, meanwhile, uses Motorcraft.
One thing to keep in mind with nearly every modern jug of coolant you’ll come across: They’re all pre-diluted. Years ago, coolant was always sold as pure coolant, and you would have to dilute the fluid yourself with water. The pre-diluted stuff is more convenient of course, but you end up paying a lot more for less coolant.
In addition to the OE options, auto parts stores will carry several different aftermarket brands of coolant. Antifreeze and coolant manufacturers all offer engine coolant versions that they say work for specific brands or countries in general (the country a car is made in is typically a good predictor for which coolant type it takes).
But none of this helps if you forget the process in a few years’ time. So, keep notes on the coolant you used and when, so you are prepared when your engine inevitably needs flushing a few years down the road.
The Correct Engine Coolant Mix
If you are buying pre-mixed coolant then go with what is in the container. If you decide to purchase concentrated anti-freeze to be mixed with water then the ratio is important.
Choosing a concentrated antifreeze can be a little more complicated. However, it gives you more flexibility when it comes to the mixture. For example, a mixture of 30:70 (30% antifreeze and 70% water) can work properly in more moderate climates. But in climates where the temperature regularly falls below 0℃, a higher amount of antifreeze in the coolant is required. Mixtures with a ratio of 50:50 work almost in every climate. In climates where temperatures drop below 0℃ for a longer period, mixtures closer to 60% antifreeze and 40% water are better suited to keep coolant from freezing.
Even if you are not driving your car in the winter months the correct engine coolant mixture is important.
