Why does engine coolant come in different colors?

Engine coolant is one of the essential fluids in your car’s engine, without it, the engine would overheat and seize due to the extremely high temperatures that engines can reach. Over time, you will have to replace this fluid as part of your car’s regular maintenance. 

You might notice that engine coolants come in different colors, the colors you’ve likely come across are green, blue, pink, and orange. These colors are used to identify certain characteristics of these fluids and while all engine coolant functions the same, you might not be choosing the right kind for your car. 

Engine coolant is there to keep your engine at a certain operating temperature, they circulate throughout the system in order to keep it from overheating. They also have anti-corrosive properties that’ll keep internal radiator components like the water pump and radiator from rusting.

In temperate and polar climates, engine coolant has the added benefit of having a low freezing point, this allows the car’s engine to reach optimal operating temperatures in cold climates, that’s also why engine coolant is called anti-freeze in areas like the U.S. or Europe.

Simply put, the reason why coolant comes in different colors is that it indicates the type of protection it provides for vehicles. In the past, coolant color was used to tell which is the right kind for your vehicle. Nowadays, coolant color is not a reliable indicator of its properties and contents so be sure to read the labels on the container to find out if it's right for your vehicle.

In the case of modern engines, it's best to seek out the coolant type indicated in your owner’s manual since it will provide the best performance and protection for your engine and radiator components. Never risk using a coolant that does not fit the parameters set by the manufacturer for your vehicle as it could cost you more than just a flush in the long run. Going with the wrong type of coolant can be pretty damaging to your system and lead to part replacements should things go bad. 

Never, ever choose your car’s coolant solely based on its color, but, knowing what these colors mean will be helpful in determining the one that you should put in your car. There are three different types of engine coolant out there with different properties and uses, some vehicles, especially newer models, can only use a certain type of coolant so pay attention to what kind you’re getting.

If the coolant your engine uses is unavailable in your area, there are universal coolant variants available that could match your vehicle’s requirements or at least come close to it.

The three types of coolants are:

Inorganic Acid Technology (IAT)

Coolants of this type were commonly used by cars produced in America from 1920 all the way to 1990. IAT-type coolants came in bright green or blue colors. This coolant contained silicates and phosphate corrosion inhibitors to protect the metal parts it comes in contact with like the engine and radiator, these coolants need to be flushed every two years or about 4800 km.

IAT coolants are outdated by today's standards and were used by American brands like GM, Chrysler, and Ford in their vehicles manufactured before the mid-1990s. If you own a car like the Ford Granada V6 or other American cars that are about the same age, this is the kind of coolant that goes with it. In short, older cars would prefer this coolant, but availability could be an issue. 

Organic Acid Technology (OAT)

OAT-type coolant can be found in newer cars sold around the world. The coolant of this type typically comes in shades of pink, orange, bright red, blue, and dark green. Organic Acid Technology or Organic Additive Technology uses Carboxylic acids instead of silicates and phosphates to inhibit corrosion.

OAT coolant or antifreeze is recommended to be flushed every 10 years or about 217,000 km. While it’s possible to get away with using this coolant for older vehicles, you should check your owner’s manual or consult with a local dealer or an experienced mechanic to ascertain if it's safe to use in order to prevent breaking vital engine components and clogs.

OAT-type coolants are now used by a majority of car manufacturers worldwide, so if you’re driving around a recently manufactured car, chances are that it likely uses Organic Acid Technology coolant.

Hybrid Organic Acid Technology

These are a mix of IAT and OAT coolants used in some new cars. The term hybrid is used because HOAT coolant has added silicates that increase aluminum protection from corrosion. On top of that, additives are also present in this coolant to prevent rust from forming. These hybrid coolants come in yellow, turquoise, pink, blue, or even purple colors.

HOAT coolant is recommended to be flushed out and replaced every five years or about 241,000 km. This coolant type is present in major European, Asian, and German brand vehicles.

Do’s

When replacing your car’s coolant, always refer to the manufacturer's recommended fluids, the same goes for every other vital fluid in your car, even fuel. You can find the manufacturer's recommended fluid in your car’s manual. If for some reason you don’t have a manual on hand, you can always check online for a copy of your car’s owner’s manual or head over to your local dealer and consult them about your vehicle.

As a rule of thumb, always check the label of the coolant container if it's suitable for your car, regardless if it's the same color or not. In addition, here in the Philippines where the climate is usually hot and where cars usually idle in standstill traffic, it's not a bad idea to have your system flushed a little earlier than recommended.

Heat and traffic are the enemies of the engine, so keeping your car’s engine cooling system in top shape is key if you want to keep your car out of the mechanic’s service bay.

Don’ts

Never mix two different coolant types together. Mixing OAT and IAT-type coolants doesn’t make them into one super coolant nor does it boost their individual benefits. Usually, mixing OAT/HOAT with IAT coolant only reduces its effectiveness and lifetime in your engine. In severe cases, sources say that mixing the two can form a sludge that can gum up your radiator’s pipes.

While mixing green IAT coolant and blue OAT coolant could result in a pretty cyan or turquoise color, the resulting bill from an overheated engine is an ugly sight to look at, so we highly advise you to refrain from mixing coolant types and colors.