If you put a little or around 1 quart of transmission fluid in the oil, nothing serious or harmful happens to your vehicle’s fuel system. But, putting a large amount, 2-3 quarts of fluid in the oil, may hurt your engine and reduce its performance.
That’s the gist of the overall situation you may face if mixing transmission fluid with engine oil. But there are lots of things behind the scenes.
So, we love discussing it from different angles, especially fluid and oil mixing ratio and intention.
Before that, let’s learn about transmission fluid and engine oil a little as it helps you to understand the whole concept clearly.
What Is Transmission Fluid?
The fluid, which lubes the gear system crankshaft, position, bearings, and other gear trans is known as transmission or hydraulic fluid. It is used to ensure the vehicle’s transmission’s optimum performance.
Transmission Fluid Types
There are mainly two types of trans fluid. One is based on transmission types, and another is based on formulation.
Transmission-type fluids are
- Automatic Transmission Fluid (ATF)
- Manual Transmission Fluid (MTF)
- Continuously Variable Transmission Fluid (CVTF)
Formulation type fluids are
- Full Synthetic Transmission Fluid
- Synthetic Transmission Fluid
- Semi-Synthetic Transmission Fluid
- Conventional Transmission Fluid
What Is Engine Oil?
Engine oil is also known as motor oil. This oil is formulated to use lubricant engine’s various parts to keep the system cool, increase heat resistance, and protect the engine against rust and corrosion. It comes with antiwear additives and detergents to improve the viscosity index.
Engine Oil Types
There are 2 basic types of engine oils. One is based on the oil’s formulation, and another is based on the engine type. Such as
Formulation based engine oil
- Synthetic Engine Oil
- Synthetic Blend Engine Oil
- High Mileage Engine Oil
- Conventional Engine Oil
Engine type-based engine oil
- Gasoline Engine Oil
- Diesel Engine Oil
- 4-Stroke Engine Oil
- 2-Stroke Engine oil
Is Oil And Transmission Fluid The Same
The straightforward answer is no. Engine Oil and transmission fluid are different. Oil works as a lubricant and trans fluid to supply power from the engine to the vehicle’s hydraulic parts and rear wheels.
As these aren’t the same, isn’t it a good idea to learn their differences? Let’s discuss
What’s The Difference Between Transmission Fluid And Engine Oil?
In general, trans fluid and engine oil are designed to serve different purposes, look different, and function differently. Some most common differences are their appearance or color, viscosity grade, and lifespan.
1. Color
Here, the engine oil looks a honey-like amber color when fresh. But, it turns dark brown or black when it contaminates and needs to change.
But the trans fluid looks red, dark green, & green, and translucent based on its type.
2. Viscosity Grade
Motor oils or trans fluid are graded by viscous to identify what oils perform in what conditions.
Some of the motor oil’s common viscosity grades are SAE 0W-30, 5W-20, 5W-30, 10W-30, 10W-40, 15W-30, 15W-40, 20W-40, 20W-50, 25W-60, etc.
On the other hand, trans fluid viscosity grades are 70W-90, 75W-90, 80W-90, 75W-140, 80W-140, etc.
3. Lifespan/Oil Changing Interval
In most cases, engine oils have a life shelf of 3k to 6k miles. After driving this mileage, you need to change the oil. But, it can improve up to 10k miles with efficient driving.
Trans fluids’ lifespan is around 30k to 60k miles, even in some cases 100k miles.
Now you have a clear idea about where trans fluid and engine oil differ. So, let’s talk about their mixing.
1 Quart Of Transmission Fluid In Oil
Adding 1 quart of transmission fluid in oil won’t negatively impact your vehicle’s motor oil’s working ability.
So, there is nothing to worry about, if you put this amount of fluid in oil.
Here Are 2 Logical Grounds To Justify The Statement.
- If the engine oil and trans fluid are from the same manufacturer and base (as discussed above), they will properly mix but won’t contaminate the engine oil. So the oil can lubes the engine’s internal components the same way as before.
- Most vehicles can hold a maximum of 5 to 6 quarts of engine oil. If you mix 1 quart of trans fluid, that means it’s about a 4:1 or 5:1 ratio. If we convert it in percentage that will be 16.66-20% of trans fluid whereas 80-83.33% is engine oil. So you can understand, the majority of the liquid is engine oil.
That’s why putting a small amount of transmission fluid in oil won’t affect your car, truck, ATV, UTV, or other vehicles.
A Large Amount Of Transmission Fluid In Oil
Putting a large amount or more than 1 quart of transmission fluid in the oil will severely change the engine oil’s chemical composition, viscose, and lubing power.
So, if you add too much trans fluid into the oil, it gradually leads to catastrophic engine failure.
Don’t you need to just blindly rely on our words. Instead, know the reason and how it contaminates the oil.
- Assume…
Your vehicle manufacturer recommends synthetic engine oil, and you pour it. And you also pour synthetic blend transmission fluid into the engine oil tank.
What happens to the reservoir?
Surely, the engine oil will lose its weight, lubing, cleaning, and protection abilities. So, when it flows to the engine system, it fails to optimize the engine as required. As a result, the engine struggles to offer you maximum performance.
- Another thing is the engine reservoir can hold 5-6 quarts of oil. But if you put 2-3 quarts of trans fluid in the reservoir, it mixes with the engine oil. In simple calculation, there is approximately 50:50 engine oil and trans fluid.
That means now the liquid is no more pure engine oil. It becomes something in between motor oil and trans fluid. So, it can’t offer you either engine oil or trans-fluid service, which is completely a waste of both.
So, vehicle or oil manufacturers, expert car engineers, mechanics, and pro drivers, everybody prohibits adding large trans fluid in oil.
What Happens If You Accidentally Put Transmission Fluid In The Oil
First, it doesn’t make sense that you accidentally put trans fluid in the oil, or internationally. Instead, the amount of fluid makes greater sense.
Little is no big deal, whereas large amounts may change the game, as there is a high chance of damage to the engine.
However, knowing that just making the engine damaged thrives your curiosity.
How does it damage right?
Here is how.
1. Change Chemical Composition
Motor oils come with phosphorus and zinc as additional additives to keep the oil clean even in driving the car under harsh weather and high mileage.
Trans fluids come with chemicals that help lubes trans gear internal mechanisms to smooth shifting.
But when motor oil mixes with trans fluid.
Both of them lose their originality.
So, the engine oil’s chemical composition will change and can’t provide promising (wear and tear protection, mileage performance, and cleanliness) benefits.
2. Change Viscosity Grade
When you mix transmission fluid with engine oil, think about what happens. The oil’s viscosity will dramatically change.
So, you can’t determine the liquid viscosity. So it will fail to flow as it can in its factory position.
3. Forms Sludge In The Oil
Sludge and deposits are one of the major culprits for oil breakdown. Though over time, sludge forms in the oil. But, when trans fluid and engine oil mix, it promotes sludge formation. Even your driving patterns also add fuel here.
Stop-and-go driving, too short trips that reach full operational temperature, prolonged idling, towing, airborne dirt ingestion, fuel dilution, and water condensation that oxidized oil makes sludge in the oil.
The sludge will clog and narrow oil passage spaces that restrict oil flow to the engine’s vital parts (especially the upper valve train area).
So, this sludge increases the engine’s wear and tear.
4. Increase Fuel Cost
Adding fluid into the engine oil incredibly reduces their lifespan. Because the oil isn’t as pure as it was before mixing trans fluid. So you can’t drive as many miles as you expect, which indirectly increases fuel costs.
Why Would People Use Transmission Fluid In Oil?
There was a myth in the past that trans fluid contains a great cleaning agent that can clean motor oil.
- So many car enthusiasts and engine maintenance DIYers intentionally added small amounts of trans fluid in oil during oil changing. Their motto was to keep the oil, reservoir, and other components clean.
- Another reason for doing so was that most engine oils in the past weren’t as good as now.
As sludge contaminated the oil and remained in the oil tank after draining. People believe adding trans fluid would solve the issue by bringing them out from the tank during an oil change.
Is It Worth Adding Transmission Fluid In The Oil?
Absolutely not. Adding transmission fluid in the oil isn’t worthy from any ground. For example
- Engine oil itself contains good cleaning agents to keep the oil clean. So, there is no need to put a small amount of fluid in the oil.
- Trans fluid is more expensive than engine oil. So it requires a large investment.
- Trans fluid shelf life is larger than engine oil. That’s why there is no reason to add the fluid and reduce its lifespan.
Why Are So Many Questions Centered Around ‘Accidentally”?
Negligence is the root cause of coming to these types of questions accidentally.
To avoid accidentally mix transmission fluid and engine oil, you have to follow the below tips.
- You must be careful about your expensive and favorite car, even for tiny deals.
- Read the user manual you received when buying your car to know about its parts, oil requirements, and other related issues.
- Read the oil container’s label to justify whether it matches your car. And then finalize the oil and use it.
Can You Mix Motor Oil And Transmission Fluid For Recycling
No, you can’t. In most cases, mixing motor oil, antifreeze, or brake fluid with transmission fluid isn’t recommended for recycling. Because all of these are designed to serve different purposes. When they mix, they lose their origin and sometimes become dangerous, which can lead to engine damage.
Big No To Putting Transmission Fluid In The Oil
Though fluids or oils are lubing liquid, they will suit some specific space and purpose. Unlikely, mixing them is a waste and can damage the engine.
So you should avoid following this horrible myth to add trans fluid in the oil to keep it clean.
Hello, I’m Gary. Welcome to my blog.
Complete graduation from Weber State University ( Department of Automotive Technology)
I have been working with automotive for about 17 years. I have a garage in New Jersey.
In my spare time, I love to spend time with my family. Driving new cars is my hobby.