You will find so many colors and types of coolant filling the shelves of your local auto parts store that it may even be overwhelming trying to choose the right one for your vehicle. However, each type serves a function to accommodate various engines and their climates.
We will clarify coolant labels so you can select the right antifreeze/coolant to keep your engine operating temperature at its optimal level.
What is Engine Coolant?
The gasoline or diesel engine in your automobile produces the power to propel you down the road.
At the same time, that engine produces a large amount of waste energy in the form of heat that must be extracted from the engine’s internal mechanisms and efficiently released to the outside air.
How does that happen? If you are driving a VW Bug, a Chevy Corvair, or a Porsche, you are likely driving a “water” cooled engine.
Your car will have an engine with internal water passages, a water pump, a heat exchanger called a radiator, and a bunch of flexible hoses connecting everything together.
How does all this work? When the engine is running, a water pump circulates cooling water through the engine and out to the radiator. The hoses carry the water.
Every time you drive, the water picks up heat from the engine to dump that heat into the air flowing through the radiator, so that your engine does not overheat.
In the description above, water is the term used for the cooling liquid. The cooling liquid, however, is not just water but a mix of water and antifreeze. The technical term is coolant.
Simply put, coolant is the liquid that cools the engine in your vehicle. To understand automotive coolants today, we must first look at the attributes of the pure water that served to do this in the past.
Water has some very positive attributes for cooling an engine.
- It has a high specific heat value. That is, water can hold more heat per unit volume than almost any other fluid.
- It has a sufficiently high boiling point.
- It is readily available at a very low price almost everywhere.
In the early 1900’s when engine driven, self-propelling vehicles came on the scene, there is no question the above three constraints made water the best of options for a coolant.
But there are several negatives with only using water, which make it then and still less than ultimate coolant.
- Water has a freezing temperature of 32 degrees Fahrenheit, which makes it unusable for engines in most northern latitudes around the world.
- Worse yet, water expands when it freezes. This fact can crack any engine that is cooled only with water in winter. It can also freeze in a radiator and easily destroy that expensive component.
- Water promotes corrosion (creates metal oxides – rust) with the materials used to make radiators or components of engines.
Very early in our understanding of how engines utilized cooling with water, chemists started altering the water with added chemicals to help offset the negatives of water and, at the same time, maintain the positives of water to cool engines.
These additives were aimed at composing a blend of water and chemicals/coolants to both offset the negatives of using water and still give the positives of water.
What is Making Water the ‘Ideal’ Coolant
When engines were first made to run at higher and higher temperatures over a hundred years ago, the big problem was freezing of the coolant. Quickly chemists found that methyl alcohol (methanol) could be added to water to lower its freezing temperature. Methyl alcohol was the first coolant additive called antifreeze.
Sadly, methanol also lowered the boiling temperature of water; thus a new and major issue was introduced. Fresh water boils at 212°F.
Engines were built to operate at or above this 212° range and will boil away water easily. There was no toleration for a lowered boiling point, in using methanol for antifreeze.
Next came glycerol, a chemical that could lower the freezing temperature of water. Glycerol could only be effective down to -36°F, but we still needed something better.
In 1926, chemists developed a chemical from petroleum, which proved to be an enduring solution; ethylene glycol.
When mixed with water, ethylene glycol not only lowered freezing temperature sufficiently, but also increased boiling temperature. It became the antifreeze of choice for combustion engines.
Huge caveat: Ethylene glycol has about one-half the specific heat value of water. So, if we add ethylene glycol to a given volume of water, we reduce the amount of heat that this coolant mix can hold.
Cooling systems need to pump larger flow rates of this coolant to transfer the same amount of heat that water alone could carry.
Pure ethylene glycol is sweet to taste as well as toxic. If you spill your car’s coolant with this antifreeze blend onto your driveway, you will have a toxic puddle.
The neighbor’s puppy might be attracted to the taste and lap it up to sad consequences. Clean up such spills, and avoid this kind of disaster.
Propylene glycol has been developed as a second and more recent option for antifreeze. It works well for automotive coolant purposes and is non-toxic in moderate amounts.
However, propylene glycol is prone to bacterial and fungal growth over time when used in coolants. Additives prevent such growth.
In 2012, US antifreeze manufacturers agreed to add a bitter tasting chemical to their antifreeze products, to reduce the toxicity claim. However, this has not been completely successful.
For these reasons, the use of propylene glycol has been inclusive. The chemical glycerol, which was an automotive antifreeze stop in 1926, has recently been reconsidered as an alternative non-toxic replacement for ethylene glycol.
Antifreeze manufacturers use proprietary additives to lengthen antifreeze’s useful life, prevent corrosion, improve water pump function, and prevent foaming.
The antifreeze smell you may have noticed under the hood is from tolyltriazole, a common corrosion inhibitor. The benefit of this additive is that antifreeze leaks are often easy to identify with a good nose.
Does It Matter What Kind of Coolant I Use?
Yes, it absolutely matters.
Your car or truck’s owner manual will give you specific information in this regard. If you don’t follow this information, you might be looking at a big repair just a few miles away.
Different Types of Coolant
One service station had 17 different types of antifreeze for cars and trucks. We will try to break this down to the types of antifreeze and antifreeze colors you may find out there in the marketplace and at parts stores.
You will also face a choice of full strength or perhaps a 50 percent antifreeze and water mix.
Full strength antifreeze will mean you will mix it yourself with distilled water before installing the coolant into the cars cooling system.
Usually, a 50-50 mix for winter climates will protect against freezing down to -35° F. If you live in an extreme cold area you might want to try a more antifreeze at 60-40 per cent mix with water for lower temperature freeze protection.
Never mix antifreeze with tap water as the dissolved chemicals and/or chlorine in drinking water can form serious cooling system issues. Always use distilled or reverse osmosis purified water for your coolant mixture.
Also, never refill an empty cooling system with 100 percent antifreeze, i.e., antifreeze with no water included, as adding 100 percent antifreeze now will freeze at approximately 10°F as compared to a 35-degree benefit from adding a 50-50 mix.
Along the way, let’s return to the discussion of colors and types of antifreeze. Coolants are dyed and tinted as a way to identify the coolant in the cooling system of an engine.
The color will help us identify the corresponding requirements should we need to add a coolant to the engine cooling system in the future, and the loss of color may help us identify a coolant that has reached the end of its useful purpose.
#1. IAT (Inorganic Acid Technology)
Typical Color: Bright Green
IAT is the oldest coolant blend and was offered by all domestic car manufacturers until around 1994; however, some manufacturers, such as Ford, continued through 2002. Asian and European car makers stopped using IAT around 1990.
IAT coolant contains phosphates and silicates and works fairly well in cast iron engine blocks with copper or aluminum radiators. IAT coolants must be flushed and replaced every 2 years or 36,000 miles.
If IAT coolant is neglected and stays in the engine, eventually solids will form-be clogging the radiator and/or engine cooling passages, bringing the cooling system performance down.
Years ago, many heater cores were clogged with IAT coolant if it was not replaced often enough.
#2. OAT (Organic Acid Technology)
Typical Color: Orange, Red, Blue, or Dark Green
This blend has no phosphates or silicates and is in almost all domestic cars after 1994 (most Asian and European car makers used OAT coolant since 1990). OAT coolants offer the benefit of longer, extended life. Most OAT coolants last up to 5 years or 150,000 miles.
#3. HOAT (Hybrid Organic Acid Technology).
Typical Color: Yellow, Turquoise, Pink, Blue, or Purple
These coolant blends fall between the IAT and OAT types, referred to as Hybrid Organic Acid Technology (HOAT) products. HOATs are commonly installed in newer Chrysler products, as well as in many other European and Asian cars.
#4. Dex-Cool.
Typical Color: Orange
Dex-Cool, a type of OAT coolant, was developed in 1995 for GM cars. Blockages frequently occurred when owners added green coolant to systems that contained the Dex-Cool system.
Other than this, Dex-Cool is a suitable coolant, but must never be mixed with any of those other antifreeze types.
Carmaker Branded Antifreeze
If you own a late model car, domestic or foreign, the best choice for antifreeze may be to go to the dealer’s parts counter. By doing so, you don’t have to interpret the antifreeze specifications and/or usage limitations on those gallon jug labels at the parts store.
You may pay a little more, but you will know you are getting a coolant formula made specifically for your car.
What kind of coolant does MY car need?
Your car came from the manufacturer with the coolant it needs. For the rest of its life, you should use the same type. The type will be listed in your owner’s manual.
You can also get this information easily from knowledgeable auto parts professionals if you need to buy antifreeze.
Can I Mix Different Coolants?
No. Don’t take that chance. Coolant blends are definitely different.
Yes, yes – there are at least three manufacturers offering a “universal” 150,000-mile extended life coolant (in yellow). But you cannot take the risk of adding that to your vehicle’s cooling system and hoping for the best.
To play it safe, whenever you need some antifreeze is to buy the type listed for you specific vehicle.
What if you are out in nowhere land and somehow your cooling system develops a slow leak? If this happens, yes, you can always add distilled water to your cooling system.
If you are desperate, you could even add clean water from a stream/canal. That is the only choice you would have. Just know that this would be a temporary fix until you get back to civilization.
Why? Because adding that water will degrade freeze and boil-over protection. So, you should only keep your vehicle running long enough to get the system checked for leaks. Then, have the coolant mix corrected to provide protection, or flush and refill with new coolant.
Why are Coolant/Antifreeze Different Colours?
Vehicle fluids vary in color from bright pink to reddish brown, so if you ever need help identifying which is which, look at our car fluid finder chart.
With coolant/antifreeze there is a couple of basic question as to why some products are one colour and other brands of coolant/antifreeze are another colour.
Sadly, it is now no longer possible to tell a specific type of coolant by its colour only, as a coolants colour has nothing to do with the chemical components of the product. So you must take extra care to top up your car engine cooling system correctly.
In the past, when Bruce Ellis, our expert, discusses the reason for colours he suggested “In the days of yesteryear, the advanced colour of a coolant/antifreeze was determined by what based chemical(s) were used to prevent corrosion of the cooling system – therefore you could tell a lot about the coolant from the colour.
Old-style IAT coolants by colour were usually blue or green and typically needed a flush and replacement every two years or at 60,000 miles.
OAT, the next line of coolants had chemical compounds that made the product provide better protection for cooling systems and gave extended life to the coolant now called ‘Extended Life Coolants’ (ELC) and were typically orange in colour as they were an OAT combination and given a change interval of five years and/or 100 000 miles.
There are blends of IAT and OAT branded as hybrids, and that are now all one fair game because there does not seem to be any great reason for a coolant manufacturer to use a specific colour, thus means it can be hard as a consumer to distinguish what chemicals are in the coolant/antifreeze based solely on from the simple colour coding if you’re lucky, blue, yellow, green, and orange,
And therein lies the confusion – you open the bonnet of a new car and unless you’re really keen, you now have no clue what the coolant is based on, when it was replaced, and worse if you buy any second-hand car liquid car, you will not have a clue when it needs changing based on colour either.
Do I Need to Use a Certain Colour of Coolant in my Car?
If you need to top up your vehicle’s cooling system often, if you have to fill your cooling system, you should always consult your manual first to check what product the manufacturer recommends. But what if you have to top it up and there is already coolant in the tank? Do you have to use the same colour depending on what is in the coolant box?
The answer is no. Because coolants are not classified by colour anymore, it is impossible to tell you if two products will mix safely in your cooling system. One wrong move could cause a blockage that could cause disaster and a massive repair bill for the cooling system.
When it comes to topping up your cooling system again, Bruce says “say you bought a second hand car and it has pink coolant in, and you check the service record, and it says it has had a coolant service within two years, who knows whether that is aftermarket or OEM spec, how long is it going to last? two years? longer?
“The best solution when you are unsure what kind of coolant/antifreeze is in your car is to put in a universal coolant that will mix with other products.
Some premium coolant/antifreeze products, like Prestone, are coolants that can mix with other types of coolants, therefore giving you peace of mind that the products are safe to use, and that they will not cause you any issues in your cooling system.”
What does the Colour of Coolant/Antifreeze Mean?
Although we would never recommend picking coolant by its colour, it is interesting to know what the different colours refer to in a general sense. Please just remember, always check your car’s manual before buying coolant, or use a high-quality universal option.
The main coolant colours are:
Green and Blue
Green and blue were used to show the Inorganic Additive Technology (IAT) coolants, typically the almost antique stuff that contained phosphates and silicates, changed on average every two years.
Orange and Red
Orange and red were typically labelled Extended Life Coolants (ELC) said to typically have longer change intervals than IAT, generally up to five years or 100,000. The use of corrosion inhibitors and antimicrobials to reduce wear and tear typical in an engine, and give better protection.
Other Colour Coolants/Antifreeze
While yellow, blue, orange and red are the most predominate colour types of coolant/antifreeze, there are other colours, purple, pink and turquoise for example, you may encounter.
Those colours may refer to different chemical compounds, for example: a Hybrid Organic Acid Technology (HOAT) phosphate coolant, but as previously outlined, the colour in this context does not matter to the make of the liquid or itself.
Can I add new coolant to old coolant?
You absolutely can. But here’s the rule:
- The new coolant that you are adding must be the same kind and color as the old antifreeze that is in your vehicle’s cooling system. If you don’t follow this rule, YOU COULD CAUSE COSTLY ENGINE DAMAGE.
In addition, when you are adding coolant, you should always use a pre-mixed 50-50 blend of antifreeze. Keep in mind, also, most vehicles will already have a 50-50 blend installed, so your addition of this new 50-50 blended coolant would not alter the freezing and boil-over temperatures too significantly.
What Can Happen if I Use Incorrect Coolant?
If you add an incorrect antifreeze to your cooling system, you could cause coagulation of the antifreeze or the radiator, or complete system, to clog-up.
If the system is severely clogged, it cannot easily be flushed and may need to be disassembled completely to decontaminate the entire system therefore costing significantly more to repair.
An Important Caution about Pre-Owned Vehicles
Let’s say you just purchased a pre-owned vehicle that would be five years plus and/or that has more than 150,000 miles on it. The first service work you do on this pre-owned vehicle should be to drain and flush the entire cooling system and install the proper new coolant.
You may have no idea if someone has done this service on your ‘new’ vehicle. Therefore, this is an extremely good idea.