Does antifreeze go bad?

Spending your winter in the sun often means leaving your car at home in the cold. But what about the antifreeze? Antifreeze also referred to as coolant is a fluid that is used in a vehicle's cooling system. This fluid is one of the most important fluids of your car because it helps in maintaining an optimal temperature for your car's engine so that it can work properly. It is not uncommon to have leftover antifreeze after topping off the antifreeze fluid level in your car's cooling system. But what if you have antifreeze fluid that has been laying around for a long time? Would it still be good or does antifreeze go bad after a while without being used?

Does antifreeze go bad?

No, the short answer to this question is that concentrated antifreeze fluid which hasn't been mixed with water has an indefinite lifespan. This is why concentrated antifreeze doesn't have an expiration date. So if you keep antifreeze in its original container with a lid on top it will be as good as new after years ready to be put inside your car's cooling system. But if you have a container of premixed antifreeze that comes mixed with water then it is going to go bad after 3 years.

So if you have any leftover antifreeze or coolant fluid after filling your cooling system you should be able to reuse the same fluid after 5 and even 10 years. But there are some guidelines for storing antifreeze for later use because improperly stored antifreeze might get contaminated by environmental elements and lose its ability to stop water in the vehicle's cooling system from freezing. That is why in this article we are going to explain how long unused antifreeze stays good and how to properly store antifreeze for later use.

Does antifreeze have a shelf life?

The shelf life of antifreeze depends upon whether it is the premixed type or concentrated type. Here is why premixed and concentrated antifreeze has different shelf lives:

Concentrated antifreeze shelf life:

Concentrated antifreeze as the name suggests does not have water already mixed with it from the factory. Concentrated antifreeze consists mostly of a chemical ethylene glycol which is then mixed with water before being added to the cooling system of the vehicle. Ethylene glycol is very stable and therefore concentrated antifreeze doesn't have an expiry date stated on it given that antifreeze is not contaminated with any dirt or other fluids during the time it is being stored. Because as soon as the water is added to the concentrated antifreeze it starts to degrade over time and doesn't stay as stable when mixed with water. Therefore if you want to store antifreeze fluid so you can use it after a long time, then concentrated antifreeze is an ideal choice for you as it can stay on the shelf for more than 5 years without losing its antifreeze abilities.

Premixed or 50/50 diluted antifreeze shelf life:

This type of antifreeze as the name suggests comes with the correct amount of water added to it from the factory. While it is more convenient to use a premixed antifreeze since you don't have to measure and add the right amount of water to it this type of antifreeze liquid can't be stored as long as concentrated antifreeze because it has water added to it already. So technically if you don't use a premixed antifreeze container within, the water that has been added to it is going to slowly degrade the antifreeze. So it is recommended to use the premixed antifreeze fluid within 3 years of buying it.

How to store antifreeze properly?

If you have antifreeze fluid leftover from a recent refill you would want to store it properly to make sure it is still useable by the time you need to top off your radiator fluids again. Therefore it is important to make sure you take necessary precautions when storing antifreeze for a long time. Not to mention that antifreeze fluid is extremely toxic so you should follow the guidelines provided below to safely store antifreeze fluid for later use:

Store the antifreeze in its original container:

Once you are done adding antifreeze to your car's cooling system make sure you store the remaining antifreeze in its original container that it came in. That is because antifreeze containers have an airtight lid that prevents any moisture and other contaminants from entering the container.

Store antifreeze in hard to reach places:

Before you store antifreeze, make sure that there is no fluid on the outside of the container. Wiping the container with a cloth before storing it is going to make sure that children or pets don't accidentally come in contact with the spilled antifreeze fluid because it can be toxic if ingested.

Label the antifreeze container with permanent ink:

The label on the antifreeze container is going to deteriorate eventually during storage and it can be difficult to identify the container without the label on it when you need it again. Therefore it is a good idea to label the antifreeze container to make sure it doesn't get mixed up with other containers in your garage shelf.

After how long does antifreeze go bad inside the car?

Antifreeze starts to degrade once it is added to the cooling system of the vehicle. Manufacturers recommend replacing the antifreeze coolant at different time intervals depending upon the make of the vehicle and the purpose it is used for. For example, if a car is used for towing or other heavy-duty uses, its engine is going to produce a lot more heat, therefore, its antifreeze will need to be changed earlier. Or if you are using a vehicle in very hot weather it is also going to make the antifreeze fluid go bad quicker.

Therefore it is recommended to test your antifreeze fluid after every 50,000 miles to see if it is still effective or not. Any mechanic can do a simple test to see if your car's antifreeze fluid has gone bad or not. But with that being said most modern antifreeze fluids are meant to last up to 150,000 miles with ideal use. So it doesn't hurt to get the quality of your vehicle's antifreeze fluid tested once it has been driven more than 60,000 miles on the same fluid.

How to test the quality of antifreeze fluid in your car?

 You can do some visual tests yourself to tell whether your car's antifreeze fluid has gone bad or not. To check the quality of antifreeze fluid in your car you can follow these steps:

Step 1.

Safety first! Always test your car's antifreeze fluid after it has properly cooled down preferably after the car has been off for more than 12 hours. This will make sure that you don't accidentally come in contact with hot radiator fluid. Remember that antifreeze is enclosed inside a sealed cooling system and when this system is hot fluid is pressurized and opening up the radiator cap to test the quality of fluid while it is hot can cause the antifreeze to spray on you.

Step 2: Check the color of the antifreeze

Most modern vehicles have a reservoir to store coolant when it expands and you can check the colour of the antifreeze fluid to make sure it is not rusty in colour or whether it has particles floating in the antifreeze reservoir. If you notice that antifreeze is rusty in colour and has particles floating in it then it is a sign your vehicle's antifreeze has gone bad.

Step 3: if there is no reservoir open the radiator

If your car doesn't have a reservoir you will have to open up the radiator cap to check the quality of antifreeze. Once the radiator is warm to touch, press down on the radiator cap and turn it anticlockwise to loosen it up. If antifreeze levels are very low or the color of the antifreeze has turned rusty or muddy you should replace the antifreeze fluid immediately.

– Use an antifreeze test strip

You can also use an antifreeze test strip to check the quality of antifreeze in your car's cooling system. To do that you will need to get a test strip from your local auto store. To perform the test simply read the instructions on the test kit to find out which color change indicates that the antifreeze is good and which ones indicate that antifreeze has gone bad. Now simply insert the test strip in the radiator so that the strip is dipped into the antifreeze fluid for the recommended period. Once you take the test strip out the change in the color of the strip will tell you if you can still use the antifreeze in your car or not.


While antifreeze is meant to last a very long time in a container, as soon as it is inserted into the cooling system of the car or mixed with water the clock starts to tick and the degradation of the antifreeze fluid starts. But in the end, it is the quality of the antifreeze that determines how long it will last in storage and inside your car's cooling system.