What Causes Engine Oil Oxidation? What You Need to Know!

We all know the smell of fresh engine oil, well it is safe to say that it fades over time as the oil oxidizes. Let’s start by saying that oxidation is known to be a natural process that takes place when the oil is exposed to air, and this is said to be one of the main reasons behind engine oil needing to be replaced on a regular basis.

But, what is it that causes oxidation in engine oil? Well, in this article, I’m going to discuss everything you need to know about oxidation in engine oil and how you can prevent it from happening.

What Causes Engine Oil Oxidation?

What Causes Engine Oil Oxidation

As I’ve mentioned above, oxidation is considered to be a natural process that occurs in engine oil over time, which results in the oil breaking down and becoming less effective. There are usually several factors behind this and down below we have listed them.

Exposure to Oxygen

This is widely known to be one of the main reasons behind oxidation in engine oil. As soon as the oil becomes exposed to oxygen, it then starts to break down which results in sludge formation. This can lead to many different problems with your car which includes a decrease in performance and an increase in wear and tear.

To prevent oxidation from occurring, you should try your best to keep your engine oil clean at all times and free from all contaminants. We think it is best to change your engine oil on a regular basis and keep up with the maintenance schedule to be on point.

High Temperatures

This is another reason for oxidation in engine oil. The thing is that when the oil becomes hot, the molecules begin to break down which eventually leads to a problem. Also when the oil oxidation temperature gets high, it may start to oxidize. This is why it is very essential to keep your oil topped up as this will prevent oxygen from having a chance of getting in.


Moisture is without a doubt one of the culprits behind oxidation. Whenever you start your vehicle in cold climates, it opens ways for condensation to form inside the engine and mix with oil, which leads to oxidation.

Another thing you should keep in mind is that when your engine reaches high temperatures, moisture is then released from the combustion. At this point, it mixes with the oil causing it to slowly break down. In some cases, water can cause sludge to build up in your engine.

To lower the risk of moisture-induced oxidation, you should take the time to check your oil level regularly with an oil dipstick and ensure that the levels are always topped off. You should also avoid running your car for an extended period in idle mode as this will cause a large amount of moisture to form inside the engine.

Oil Age

Let’s not forget that the age of the oil will play a role in affecting its stability. However, as time goes by, the oil will degrade which is caused by moisture, oxygen, and heat. As you already know, oil ages as soon as it is exposed to oxygen.

There is no doubt that fresh oil is always the best. As your oil ages, its lubricity becomes lower as well as its ability to protect your engine from wear and tear. So, make sure that you check your oil and ensure that it is changed regularly to avoid any issues over time.


One thing for sure is that engine oil can become contaminated with various things such as dirt, and other debris, which can actually lead to a catalyst for the oxidation process. This usually comes from several factors such as moisture, rust, corrosion, fuel, and oil leaks.

These contaminants may result in the oil heating up and breaking down causing oxidation to occur.

How to Prevent Engine Oil Oxidation

Engine oil

Your engine oil is very important as it helps to keep your car running smoothly, so it is essential that you keep it clean. The thing is that your engine oil tends to become oxidized as time goes by, reducing its effectiveness.

Another thing to keep in mind is that oxidation can occur due to high temperatures and oxygen, which will eventually lead to a decrease in lubrication and an increase in sludge. If you aim to make sure that your engine oil remains in the best condition possible, you may want to follow these steps:

Regular Oil Changes

The most effective way to prevent engine oil oxidation is to change the oil at the recommended intervals. What this does is ensure that fresh oil is always circulating through the engine and helps to prevent any form of contamination from building up.

Use Only High-Quality Oil

We only recommend that you use high-quality oil, especially the ones that are made for your vehicle as this will prevent oxidation. We think the synthetic or synthetic blend would be the best option since these types are known to be more resistant to oxidation.

Avoid Idling

You should not allow your vehicle to stay idling as this causes the engine to run at low temperatures, which may eventually lead to an increase in oxidation. As you can see, it is not recommended to idle for long periods, as it is not good.

Ensure that the Engine is Clean

You should make sure that the engine is always clean since a dirty engine may cause the oil to become contaminated, which can eventually lead to oxidation. This is why it is important to keep the engine clean by taking the time out to wash it regularly and removing all build-up dirt and debris.


As you can see, oxidation in engine oil can cause by a variety of things. In this guide, we have mentioned everything that may cause oxidation in engine oil and the most effective way to prevent it from happening in the first place.

We truly hope you find this article helpful! You can also check out the other guides on this site, thank you.