Can I Use Motor Oil For Transmission Fluid?

Motor oil and Transmission fluid are both essential fluids needed for the optimum functionality of your vehicle engine system. The motor oil is designed to function in the engine, while the transmission fluid is meant for your steering and gear system. These two fluids have certain similarities, but can I use motor oil for transmission fluid? The simple answer is No. Don’t attempt that.

We’ve discovered that a lot of people confuse these two types of fluid and misuse them in their vehicles, which has made them suffer from severe engine damage. Take a look at this for a second; if you can easily interchange these fluids, then there is practically no need to produce both of them. One can do the trick. Well, this is not the case. Various striking differences define transmission fluid vs. engine oil.

That’s why we’ve constructed this guide to give you a clear difference between motor oil and transmission fluid and let you know the right system in your vehicle to apply these fluids.

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Difference Between Motor Oil And Transmission Fluid?

The motor oil’s function is to improve sealing, prevent rust on various engine components, keep the engine parts sludge-free, cool the engine system, and reduce the friction between mobile parts in your engine system. On the other hand, the transmission fluid helps to improve the operation of your auto or manual transmission.

The key difference between these two fluids is that the motor oil functions are directed to the engine area that handles combustion. In contrast, the transmission fluid lubricates your vehicle’s transmission system, allowing your clutches and gears easy engagement. If these fluids are mistaken for the other, can motor oil ruin a transmission system? Of course.

Motor Oil vs Transmission Fluid

transmission oil vs engine oil

1 Function This fluid operates in the engine system, which helps to eliminate high friction between moving components in the engine system and keeps the system rust and sludge-free. The Auto transmission fluid (ATF) functions majorly in the transmission system of a vehicle. This fluid ensures the smooth operation of gears and clutches within the transmission system.
2 Rate of Consumption Motor oil reduces due to mileage and time. Always check the motor oil before starting your vehicle. Transmission fluid does not reduce as much with time or mileage. It is not normal to have a low transmission fluid level within short periods. If you notice this, you should inspect your system for any leaks immediately.
3 Color The color of motor oil usually matches a golden or bright yellow color when unused but turns black after being used for some time. The usual color of most transmission fluid is red.
4 Life span You have to change the motor oil every 3000 to 6000 miles; it can be more, Depending on Oil Type. If the oil stays longer, it will lose its properties. Ensure you always change the motor oil timely. This fluid does not need to be changed regularly; it can last for a longer period between changes.
5 Detergents Motor oil consists of a fair number of detergents. Transmission fluid is produced with a high number of detergents because they work in a more contaminated environment.
6 Viscosity It is highly viscous and made to function under high temperatures and pressure. It is less viscous and designed to operate under a reduced temperature and pressure.

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What Happens If I Use Motor Oil For Transmission?

If you put engine oil in transmission fluid, you will notice any of the adverse effects highlighted below. However, the damage extent depends on the quantity of engine oil added and how long the vehicle has been driven with the wrong transmission fluid.

Grinding sensation in gear

The automatic transmission system is designed to function smoothly with the recommended fluid, so replacing this fluid with something else entirely, like motor oil, can cause adverse effects on your transmission system. You will start experiencing grinding or shaking movements whenever you change gears due to either damaged seals or O-rings.

Vehicle unable to function when in gear

When there is motor oil in your transmission system, you are going to notice a delay in the response of your vehicle while in gear, or the transmission might not function when you position it in reverse or drive. This is because the motor oil properties cannot replace the functions of when you have transmission fluid in your system. So, these complications will occur.

Gears slipping

Gears slipping is another issue you will struggle with if you are a victim of this incident; it is a critical safety issue if this happens, and it can be very frightening to deal with your transmission system shifting gears while driving. This is because of the wrong transmission fluid in your vehicle system.

Burning smells

It is not normal to perceive burning smells in your vehicle, and a common cause is this smell from your transmission system is as a result of the overheated fluid in the transmission. Unlike motor oil, transmission fluid has a higher lubricating property, preventing any form of damage between meeting parts. If your transmission system is not well lubricated, it will finally lead to a total breakdown of your transmission system.

Several noises were made while driving

A wrong type of fluid in your transmission system will cause several noise forms when you drive your vehicle. When the fluid in your automatic transmission system does not have the right function, several noises will be produced from your transmission system.

The transmission fluid does a good job of keeping the mechanical gears and system well-lubricated. The absence of this function will damage your transmission system, causing the system to produce noises while driving your vehicle.

The engine check light turns ON.

The transmission system is designed with many sensors that tell if there is anything abnormal with your transmission system. These sensors send signals to your vehicle’s computer system, indicating any issue. So, if you use transmission fluid for engine oil in your system, it will trigger your engine check light to turn ON.

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How To Fix The Problems Caused By Motor Oil In The Transmission

The time you notice this error determines how easy it will be to fix this issue. If it is noticed early enough, there will be little or no damage done to your transmission system. You might just have to flush the motor oil from your transmission system, but this might not be necessary if you add a small amount of motor to the transmission system. However, if you observe any of the effects mentioned above, you should flush. We will gladly show you how to flush the system. Also, this applies to any make, model, or year of car.

Flushing the transmission system isn’t challenging, provided you have the things you need. You will need the recommended transmission fluid types, a funnel, and a bowl of some simple tools.

The first thing is to open the hood of your car. When dealing with any liquid in the car, disconnect your battery’s negative terminal to avoid shock. Now, if you go underneath the car, you will see the transmission coolant lines (it might not be necessary to lift your vehicle. You can do this without having to do that).

Ensure you have your bucket ready to hold the drained-out fluid when you detach the transmission lines. You should check your vehicle’s repair guide to know which line to take out, but if you can’t get a hold of that, you can detach the two lines with the correct screwdriver types, put them both into a bucket, and one of them should spit out the fluid in the transmission system. One thing you also need to know is that transmission oil and transmission fluid are the same. You don’t have to be confused about that.

You are going to need the same amount of transmission fluid pumping into the system. Never flush your transmission with low fluid to prevent air bubbles from accumulating in your lines, which spells trouble. Also, you do not want to run your car with a low fluid level, as it can cause the engine to knock down completely.

Now place your funnel in the transmission port and get the correct fluid ready. Unplug the transmission deep stick. Note that you have to continually fill up the funnel in the transmission port; this will make sure there is no room for air bubbles. Then you can have someone start the car.

If you have an oil gun, you can fill it with the transmission fluid and connect the hose to the transmission port so that the fluid will flow in without your effort. But it doesn’t matter, and you can use whichever you have. Immediately after the car starts, you will notice a high flow of fluid from your transmission lines. Turn your steering wheel to opposite sides to increase the flow. It is best to do this with an assistant. Observe the fluid flow, so you know the right time to stop the flush. The right time is when you notice the fluid coming from the line has a similar color to the transmission fluid poured in.

You can continue flushing for a while so you get a similar or near similar color with your transmission fluid, and then you can stop the process. Please make sure you check the transmission fluid level and do not overfill because that will only give you problems. If you did that, you should let out the excess fluid. Ensure you follow this guide correctly so you don’t have issues with motor oil in manual transmission or automatic systems.

If you have driven your vehicle for hours with the wrong fluid, then you should tow your vehicle to the mechanic’s shop to repair any damaged components and flush out your transmission system.

Final Words

With this guide, we shouldn’t be getting any more questions on whether can I use motor oil for transmission fluid or use transmission fluid instead of motor oil. They are distinct and are meant for different purposes. So, avoid having your engine oil mixed with transmission fluid. Always apply the right fluid in your vehicle and avoid dealing with unnecessary problems.

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Hi there, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I worked as a Mechanic and Mechanic Supervisor for over fifteen years at Global Rebound Automotive companies - Toyota, TATA, BMW, Nissan, TVs, and Others. Now, I enjoy my new role of leading a team of automotive experts (in their respective fields) and publish new content on a regular basis on my website and social media.

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