Can You Mix Oil Viscosities? (Explained!)

People are asking whether you can mix motor oil with different viscosities. This is important to discuss and to know. So stay and keep reading to know more about the subject.

So can you mix oil viscosities? The people have taken sides with yes and no. The majority of people will say that you should not mix two motor oil with different viscosities.

An oil change is one thing that keeps our engine running and in good condition. However, it is not just the oil change that is important. What you use as motor oil is also essential. 

You cannot just put any motor oil in your oil tank. You need to know what viscosity you must use because that is very important to your vehicle and its engine. The viscosity of the motor oil is referring to the thickness of the motor oil. 

Every vehicle has a specific level of viscosity that you should be using in your vehicle. Not using the proper viscosity level in your motor oil can cause harm and damage to your vehicle.

Can You Mix Oil Viscosities

Is It Okay To Mix Oil Viscosities?

As mentioned, if you will poll, the public will start to equalize those who will vote and those who will vote no. If you ask some people, some will answer that you can mix two motor oil with different viscosities. They will also say that it does not provide any harm to your vehicle’s engine, and you will do just fine. 

However, if you want to be on the other side, you can too. The majority, though, will answer no. Mixing two motor oils with different viscosity levels is never recommended. 

It is discouraged. You should not be mixing two motor oils even if they have the same viscosity level. So now that two motor oils do not have the same level of viscosity, indeed, you cannot mix them both. 

They also say that the idea must not be entertained even a bit. There is no reason for you to mix two motor oils with two different viscosity levels. The rule of thumb here is to follow what was on your owner’s manual. 

You should have what level of viscosity you should have for an oil change in your owner’s manual. But you should never mix the two motor oils. You can always stick to one. 

Every motor oil is produced differently. Every company has different technologies and machines, and they also have different formulations to make their motor oils. So with that, the additives that are in the motor oils will also be different. 

Only the one who works for the manufacturer knows the actual chemistry of the motor oil. So we do not know how these motor oils would affect each other and how they would be compatible or incompatible in terms of their mixing up together.

What Happens If You Mix The Viscosity Of Oil?

Some people would say that there are motor oils that are compatible with mixing. However, if you mix them, they will create another level of viscosity. This means that there is a shifting in the level of viscosity for both two motor oils. 

With that, the new viscosity level created by the mixture of two motor oils with different viscosity levels might not be compatible with your engine needs. So it is best not to mix any oil viscosities. However, some people will say that there is no effect if you will need viscose oil. 

Even if the motor oils have different viscosities, they will not separate, and they will also negatively react to one another. This is because the base oil is just the same at a molecular level. If the motor oils have different oil additive systems, then the two will not be mixed. 

There are additives on the motor oil, and these additives are antioxidants and prevent the thickening of high operating temperatures. In addition, motor oils function as protection against corrosion and rust. Finally, they work as a detergent, and as a detergent, they will remove any varnish or sludge. 

They also provide lubrication so that your moving parts will not get wear and tear from the friction. They also remove any contaminants along the way. 

With that, each company produced motor oil differently, and so the amount and the type of the additive that these manufacturers have made will differ. And if you mix two motor oils with the same or different viscosity levels, it might not function and run the way it should be.

What Is The Correct Way To Mix Oil With Different Viscosities?

There is no correct way to mix oil with different viscosities because it is never recommended. But if you have no choice and insist on mixing oil with different viscosities, you must consider that both of the motor oils must have the same brand. Always remember that the mixture of the two motor oils will create a new level of viscosity. 

They will create a product that has a different viscosity than the viscosity of the other two. But, again, it is still always the first choice to go and look for an owner’s manual. There might even be an owner’s manual that would clearly state no mixing of two motor oils. 

Again, find and read your owner’s manual. In the owner’s manual, it is always stated there are the best options for your vehicle. So there is not a specific and correct way to mix oil with different viscosities because even experts would say not two oils with different viscosities. The product might also damage your vehicle and its engine.

How Do You Determine The Viscosity Of A Mixture?

In determining the viscosity of a mixture, you can first measure a sphere’s velocity as it falls through the liquid. Then, the sphere’s velocity mixed with the relative densities of the sphere and the liquid can be used to calculate the mixture’s viscosity.


In summary, it is never advisable to mix two motor oil with different viscosities. This is because the mixing of both can alter the level of viscosity. 

As a result, it can create a new level of viscosity. But, unfortunately, the new level of viscosity might not be compatible anymore with what your vehicle needs.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more