Can You Mix Red and Green Antifreeze: A Comprehensive Guide

Car owners often ask “Can you mix red and green antifreeze in your engine?” and we understand why this confuses many people. There is always a temptation to add two different coolants, with many even believing that adding the two can give a better antifreeze mixture for their engine.

Can You Mix Red and Green Antifreeze

But can you mix the red and green ones with no consequences? Our team is here to answer this important question, so read on to find out.

Is It Advisable To Mix Red and Green Antifreeze?

No, it is not advisable to mix red and green antifreeze in your vehicle. This is because they are made with two different technologies and, hence, have different effects on the engine of the car. Generally, it is only safe and advisable to mix antifreeze with water.

Many people subscribe to the belief that “antifreeze is antifreeze,” but that is far from the truth. There are different car antifreeze or coolants, as indicated by their different colors. In other words, the different antifreeze colors are not just for aesthetic appeal but have real functional significance.

The red antifreeze uses the Hybrid Organic Acid Technology (HOAT), while the green engine coolant uses the Inorganic Acid Technology (IAT). Considering that they use different technologies, there are certain differences in their function, and subsequent use. They both work towards the same function of protecting the car’s engine from freezing or getting too hot, though. 

The red and the green antifreeze are easily the most common of all the coolants available today. However, there are other colors available, like orange antifreeze, yellow antifreeze, gold antifreeze, and blue antifreeze. Your car will use only one of these, but that’s it – just one. It is not advisable to mix green and red coolants, or any other colors of antifreeze, for that matter.

What Are the Problems of Mixing Red and Green Antifreeze?

The problems of mixing red and green antifreeze include high repair and maintenance costs, as well as a variety of engine-related issues. The exact problems and their severity depend on the amount of the red and green mixture used, as well as the type of the engine.

Below, we consider the various problems you can encounter if you mix green and red coolants. 

– Affects the Engine’s Cooling System

Normally, antifreeze, irrespective of color, flows through the engine’s cooling system to elicit its effect. However, when you mix green and red antifreeze, the ability to move through the cooling system drastically reduces.

Affects the Engine’s Cooling System

This is because the two different types of antifreeze contain different chemicals and additives.  The result of mixing these two different coolants is a thickening of the mixture, which will not flow properly through the engine’s cooling system.

Ultimately, the normal functioning of the car’s cooling system is altered, and this can cause the engine to overheat. If this issue persists, it can cause irreparable damage to components of the cooling system. 

– Lowers the Functionality of the Coolants

If you mix green and red coolants, neither of the coolant will work well, aside from the negative impact on the engine. For instance, if your car requires a green coolant and you add a mixture of red and green coolants, neither of the coolants will work well. 

Even worse, if the coolant mixture spends too long in the engine, the green coolant, which is the right coolant, may not work on subsequent occasions. There is simply no upside to mixing these coolants.

– Destroys the Cylinder Gasket

Destroys the Cylinder Gasket

The cylinder gasket seals the cylinder in the engine that holds air and fuel for combustion processes. However, a mixture of red and green coolant can destroy this gasket as the different chemicals in both coolants react to give an acidic environment. This strongly acidic environment weakens the gasket and can cause the cylinder to start leaking.


– Increases Maintenance Costs

This is implied to a reasonable degree. Since red and green antifreeze are not compatible together in an engine, they may result in several engine and car issues. Essentially, these additional issues can increase the maintenance and repair costs that the owner will spend. 

For example, red and green antifreeze can destroy the cylinder and head gasket of the engine. This means the car owner will have to spend more repairing or replacing these gaskets, and even the engine cylinder. 

Also, if the engine overheats and components of the car’s cooling system become damaged, the owner may have to replace the entire cooling system or engine. That could significantly raise the amount the owner will naturally spend on maintaining their vehicle. 

How Can You Fix the Problems of Mixing Red and Green Antifreeze?

You can fix the problems of mixing red and green antifreeze by first flushing out the antifreeze mixture, adding a new antifreeze, and then repairing any resultant issues. While it can be a stressful process to rectify the issues that arise from the wrong antifreeze combination, it is definitely doable. 

We will consider the exact steps to follow in fixing the problems of mixing red and green coolants. 

– Flush Out the Antifreeze Mixture

The first step to fixing the issue is to remove the mixture of the red and green coolants.

Flush Out the Antifreeze Mixture

Here are the steps to follow for this process.

  1. Ensure your car is in a level position and the engine is cool before attempting to replace the coolant. Place a drainage pan under the cabin to prevent any loss or spillage of coolant. 
  2. Remove the fill cap on the radiator to expose its content and then find the radiator’s drain, which is typically at the base of the radiator. You can refer to your manufacturer manual for more information. 
  3. Open the radiator drain, and allow all the coolant to drain to the drainage pan beneath the radiator. After the coolant has completely drained, close the radiator drain.
  4. Wash the radiator, either using pure water or a specific cleaning radiator product by connecting the radiator hose to a water pump
  5. You can fill the radiator and the antifreeze reservoir with water and allow the engine to run as usual for ten minutes. After the engine gets cool, completely drain the contents of the radiator again.
  6. You can take the green and red antifreeze mixture to a recycling company for proper disposal.

– Add New Antifreeze

After you have removed the old antifreeze mixture, you need to replace it with a brand new and appropriate one. Make sure you only use the recommended antifreeze for your vehicle, and you can check your owner’s manual for clarification or call a professional.

Below, we will run down the steps for adding new antifreeze.

  1. Choose the right antifreeze product. Older cars usually require green coolant, while the newer ones use the red antifreeze. However, that’s an overly simplistic classification and you should confirm the exact antifreeze your engine supports.
  2. You should only dilute with water in a 50/50 combination. That is, half of the mixture is water and the other half is the right coolant. 
  3. Fill the radiator and the antifreeze reservoir and close the caps.
  4. Warm up the car engine for a while and confirm that the reservoir is filled to the right level. You may need to add more antifreeze mixture.
  5. Close and firmly secure the radiator and coolant reservoir caps .

– Visit a Mechanic 

Sometimes, the mixture of the red and green coolant will have damaged some components of the engine and the cooling system.

Visit a Mechanic

You need to visit a mechanic to be sure that the engine is in proper condition after replacing the wrong color antifreeze combination with the right one. 


Car owners often wonder if they can mix green and red coolant for their vehicle and what consequences, if any, it may have.

We have detailed that in this article, and here are the key points to note:

  • It is not safe to add red and green antifreeze as they are made using different technologies and chemicals.
  • The effect of adding red and green coolant ranges from minor cooling problems to the whole engine severely overheating.
  • The first thing to do if you have added red and green coolant to your car is to completely drain the mixture.
  • After draining the wrong coolant combination, add a new antifreeze and water mixture.
  • Bring your car to a professional for a check-up to ensure the engine is in proper condition.

So the next time you feel tempted to add red and green antifreeze, don’t! You know better now, and your car will thank you for it.

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