Different fluids have different functions in your automobile. Some can be interchanged or mixed from the large number of fluids our car has, but not all. People often wonder whether they can combine two oils and use them for a particular part of the vehicle or not. 

Many people often doubt if they can mix gear oil with engine oil or not. We will try to clear this doubt in this article. Let’s have a look!

Also Read: Can You Use Vegetable Oil For Engine Oil?

Can You Mix Gear Oil With Engine Oil?

For mixing any two fluids, it is always better to look at the chemical composition of both of them to be on a safer side. Similarly, we must first have a look at the chemical composition of gear oil and engine oil before proceeding to whether you can mix or not.

Chemical Composition and Usage: Gear Oil

Gear oil is made of mainly two components: the base oil and the additive. Gear oil is thicker and has high viscosity than engine oil, and it is used for lubricating the gear and helps in smooth changing of gear. It also helps to cool down the gearbox and prevents rust.

Chemical Composition and Usage: Engine Oil

Engine oil is a composition of large amounts of base oil and small amounts of other additives such as detergent, viscosity additives, and other components. On average, engine oil has less viscosity than engine oil, and it ensures that the engine runs smoothly and all the parts are properly lubricated. 

Also Read: Is Engine/Motor Oil Flammable?

Now that you’ve had a look at the composition, let’s see can you mix both of them?

Is It Okay To Mix Gear Oil With Engine Oil?

Mixing gear oil and engine oil is a bad idea. Gear oil is more viscous than engine oil, and if you mix them, the viscosity of the resultant oil changes. Using the resultant oil in either gearbox or engine oil pump can harm your vehicle.

The main use of gear oil is to make the transmission run smoothly, which is why it has high viscosity. If a high viscosity oil is used in the engine, it can start damaging your engine slowly and won’t give better results. 

Also Read: How Hot Does Engine Oil Get?

Mixing them in very small quantities is fine, but in the case of a good quantity, this mixture can make your car’s engine slow.


Mixing two lubricants won’t always be a good idea. As we have mentioned above, you can just mix a very small portion of gear oil and engine oil but don’t mix them in a good quantity as this can make your car’s engine very lethargic. 

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