Can You Mix Green and Red Antifreeze?


Odds are you don’t spend a ton of time thinking about your car’s antifreeze, but having the right amount and the right type of antifreeze in your vehicle is important to ensure that your car runs correctly. The various types of antifreeze available have significant differences in terms of their chemical composition, and it’s usually not a good idea to mix two different types of antifreeze together.

This certainly applies to green and red antifreeze. If you mix these two types of antifreeze together, you could end up seriously damaging your car’s cooling system. No matter what you do, always avoid mixing two different types of antifreeze together.

In this article, we’ll be covering the differences between these two types of antifreeze in detail and explaining what exactly happens when you mix these two types of antifreeze together. We’ll also walk you through how to change your antifreeze yourself and answer some other common questions that people have about their car’s antifreeze.

What Is Green Antifreeze?

Green antifreeze is the oldest variety of antifreeze still on the market today. This type of antifreeze is classified as an Inorganic Acid Technology (IAT) antifreeze, which exists alongside Organic Acid Technology (OAT) and Hybrid Organic Acid Technology (HOAT) antifreeze.

Being an IAT antifreeze, green antifreeze has some advantages and disadvantages compared to other types of antifreeze. The main advantage that green antifreeze has over other types is the fact that it’s very effective at preventing corrosion from happening within the car’s cooling system.

However, the main disadvantage that it has is that it doesn’t remain effective for as long as other types, and will need to be changed more frequently. A fresh batch of green antifreeze should probably last you about 30,000 miles or so before it has to be changed.

Fun fact: coolant needs to be diluted to work properly, and these days all types of coolant come pre-diluted from the factory. Previously, however, you had to dilute your antifreeze yourself before adding it to your car.

Obviously, it’s way more convenient to buy antifreeze that is already diluted, but on the other hand you also used to get more value for your money with the undiluted antifreeze.  

Read: Temperature Gauge High But Car Is Not Overheating

What Is Red Antifreeze?

Red antifreeze, on the other hand, is classified as an OAT antifreeze. As such, it’s not as good at fighting corrosion as IAT antifreeze, but it will last for way longer before it has to be replaced. Red antifreeze should last about 50,000 miles or 5 years before it will need to be changed.

It’s important to note that the color of your antifreeze doesn’t necessarily determine for sure what kind it is; antifreeze colors aren’t regulated, and while most manufacturers tend to make certain types of antifreeze in certain “standard” colors, there’s no law that states that a specific type of antifreeze has to be a specific color.

For example, all of the antifreeze Honda makes is blue, regardless of what type it is. In addition, OAT coolants aren’t always red; in many cases, they’re more of an orange or yellow color. Always check the label of your antifreeze before buying it to make sure it’s actually the right kind of antifreeze for your car. 

What Happens If I Mix Green and Red Antifreeze?

You might assume that mixing two different types of antifreeze won’t cause any problems for your vehicle; after all, it’s all antifreeze, right? Wrong! While it’s true that green and red antifreeze are ultimately designed to do the same thing, they do so completely differently thanks to the fact that they’re made from different chemicals.

In fact, if you were to mix green and red antifreeze together, it would end up creating a thick gel that would fail to flow through your cooling system properly. This can cause overheating, as well as damage to various components of your car’s cooling system. 

If you do end up mixing these two kinds of coolant together by accident, don’t even attempt to drive your car. If you want to have any hope of salvaging your cooling system, you’ll want to flush your cooling system as soon as you can (which we’ll show you how to do later in this article).

What Happens If I Use the Wrong Kind of Antifreeze?

So, we know mixing two incompatible types of antifreeze together in your cooling system is a bad idea. But what if you were to entirely fill your car’s cooling system with a different kind of coolant than what the manufacturer recommends? How much damage would that do, if any?

Using the wrong kind of antifreeze in your car won’t have as many immediate and serious effects as mixing two kinds of antifreeze together, but it’s still not very good for your cooling system at all.

Manufacturers recommend using different types of antifreeze based on what materials are used in the cooling system, and if you use an antifreeze containing additives that aren’t compatible with your specific cooling system, you’re liable to wind up with a lot more corrosion occurring.

Read: What Happens If The Car Engine Coolant Is Low?

Why Are There So Many Types of Antifreeze?

At this point, you might be wondering why so many different types of antifreeze even exist to begin with. All types of antifreeze essentially do the same thing, so why haven’t manufacturers just made one standardized antifreeze for use in all cars?

Once again, the reason for this is the fact that automakers use a variety of different materials in their engines and cooling systems. Different types of antifreeze contain different additives that make them more friendly towards one type of material or another. Simply put, some types of antifreeze are optimized for specific engines.

In the case of undiluted antifreeze, the fact that there are so many types is mainly due to the fact that water quality varies greatly from place to place. The water you put into your cooling system can make a big difference, depending on factors like the mineral content of the water and its pH level.

How to Change Your Car’s Antifreeze?

If you’ve accidentally just filled your car up with two different kinds of antifreeze, or if your existing batch of antifreeze is approaching the end of its life, you’ll need to flush out the antifreeze currently in your system and fill it up with a fresh batch. The good news is that changing your car’s antifreeze is a pretty simple procedure that can be done easily at home.

To correctly change your car’s antifreeze, you’ll need to follow these steps:

Flushing Your Old Antifreeze

  1. Prepare your work area to make this task as safe and easy as possible. Start by parking your car on a level surface, and don’t attempt to change your antifreeze until the engine and radiator feel cool to touch. In addition, you should have a large drain pan on hand to catch any old antifreeze that might spill while you’re changing it.
  2. Open the fill cap on top of the radiator. Your car may also have a separate reservoir for antifreeze; if it does, open the fill cap on the reservoir too.
  3. Find the drain on the bottom of your radiator, and position the drain pan under it. If you’re having trouble finding your radiator’s drain, your owner’s manual should have that info available for you.
  4. Open the drain, and allow the old antifreeze to flow into the drain pan. Once the antifreeze has finished draining, close the drain.
  5. Grab your radiator flush product, and pour it into the radiator. Follow the directions on the product and make sure you fill your radiator up with enough water as well.
  6. Replace the caps on the radiator and antifreeze reservoir, and run your engine for about 10 minutes until it hits its normal operating temperature. Once it does, shut off the engine and allow it to cool.
  7. Open up the caps on the radiator and antifreeze reservoir, and drain the radiator flush product into your drain pan.
  8. Collect all of your old antifreeze in a sealable container and take it to a recycling facility to dispose of it.

    Read: What Happens If The Car Engine Coolant Is Low?

Adding New Antifreeze

  1. With your cooling system fully drained of the old antifreeze, refill your radiator with the new coolant. If you have to dilute your antifreeze before adding it, make sure to only use distilled water.
  2. Leave the radiator cap off, and run the engine for a little bit. Keep an eye on the antifreeze through the open cap, and replace the cap when it stops bubbling.
  3. Check the level of antifreeze in the reservoir, and add more if you have to.
  4. Make sure the radiator and reservoir cap are closed and secured. You should now be all done changing your car’s antifreeze!

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