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Is Engine Oil the Same as Transmission Oil?

Is Engine Oil the Same as Transmission Oil?

If you’re servicing your vehicle, you may be looking to save some money and get your many oils and lubricates working doing double duty for you.

Some products can be used for different parts of your vehicle, but what about engine oil and transmission oil?

Are they the same? Can you use engine oil and transmission oil interchangeably?

Engine oil and transmission fluid both decrease friction by lubricating your engine’s components. However, they’re not identical. Engine oil doesn’t stop working if it’s filled with combustion by-products. It can travel through the engine and continue working as usual. 

Automatic transmission fluid is different from the usual oil you’ll see in an engine. 

You can typically identify it by looking at its color. Most of the time, it’s either red or green, making it easy to spot. 

They’ve designed their colors to make them easy to differentiate from engine oil. 

That’s because they’ve got to lubricate other components, mainly the transmission. It’s also part of the steering system if you’re driving a car that has powered steering. 

Transmission fluid isn’t able to work if there are contaminants in it. They’ve designed cars to keep their transmission fluid in a closed network. That’s why they’re never exposed to byproducts as well. 

Modern vehicles use transmission fluid that’s made with base oil and additives. The additives change the fluid’s properties, to meet each system’s specifications. 

Some of the additives they’ve used can decrease how much you’re wearing out the engine. 

They’ve also added some to inhibit rust formation and to prevent corrosion. Adding detergents to the blend can help to make sure gunk doesn’t build up in the engine, too. 

Surfactants have also been useful as a way to prevent gunk accumulation. It’s able to keep things from sticking to metallic surfaces. 

They’ve used some to help control the fluid’s viscosity, even at high pressure. Controlling its viscosity with chemical additives helps it perform well in all environments. 

Anti-oxidation compounds have become a part of most transmission fluid blends. These prevent oxidation reactions from occurring, preventing boil-off. 

By putting that into it, you’re also able to prolong the other additives’ lifespans. 

Using cold-flow enhancers has improved transmission fluid’s ability to work in low temperatures. Most fluids have one of them in them to prevent the fluid from malfunctioning if it’s below freezing. 

Nearly all modern transmission fluids contain friction modifiers. Only a handful of transmissions designed by Ford don’t need any of it in their fluid. 

Each additive they’ve put into the fluid has been put into the formula to enhance its properties. That’s how they’ve created fluids able to perform under the demands of a modern engine. 

Can You Use Engine Oil As Transmission Fluid?

Engine oil is not able to lubricate an automatic transmission system, so don’t try using it. It doesn’t have the right characteristics to keep your transmission working.

Automatic transmission fluid entered the scene around the same time automatic transmissions did. 

They’ve designed several variations since the first ones were made by GM. They invented transmission fluid to lubricate their Hydra-Matic 4-speed transmission in 1940. 

Most of the time, you’ll never need to replace your car’s transmission fluid. That’s because they’ve designed them to remain in closed networks while they’re used.

That’s because it’s never exposed to anything in the engine. They use a hermetically-sealed design to prevent anything from getting into the fluid.

So, it can last for a long time without needing to be replaced. 

You can even find cars that have transmissions with lifetime fluid guarantees. They’re able to claim your fluid will last a lifetime as long as it lasts over 100,000 miles. 

Making sure the fluid stays in ideal conditions prolongs its lifespan. Fluid checks aren’t necessary if your transmission system doesn’t seem to be leaking. 

Opening one of them to check its fluid level could introduce unwanted contaminants. So, you shouldn’t try to check your car’s fluid unless you’ve seen signs of a leak. 

You can make sure your fluid lasts longer by using one that’s made with high-quality materials. They’ll last longer if they’ve got base oils that resist oxidation. 

We’ve seen a lot of power steering assemblies that use ATF as a hydraulic fluid, too. You can use it as a way to control power delivery from a hydraulic system. 

What Happens If You Put Engine Oil in Your Transmission?

If you put engine oil in your transmission, you would notice something wrong. Turning on the engine would force the oil through the transmission, creating friction. 

Keeping the engine on for too long would probably destroy its transmission. You may be able to drive around for a little bit, but you won’t get far. 

The longer you’ve driven, the more damage you’ll cause to your car. 

Always make sure to use the correct transmission fluid for your car. Otherwise, you could completely wreak your transmission, meaning you’ll need a new one. 

Replacing the transmission system on a car could cost you thousands of dollars. That’s why it’s so important to always use the right fluid. 

Getting the wrong fluid into your transmission system could lead to permanent damage. 

A mechanic may not be able to repair one that’s had the wrong fluid put in. 

Another sign you’ve put in the wrong fluid would be burning smells. The wrong fluid won’t decrease friction as much. All that friction can make it smell like something is burning inside the engine. 

You’ll always be able to tell by paying to attention to your gears. Listen to them whenever you’re switching to another gear. If you hear one of them slip, you’ve put in the wrong fluid. 

Once they’ve made it into the right spot, they might start grinding

Transmissions need the right fluid to work without grinding while you’re using them. It could even make it feel like the car is shaking if you keep driving. 

One of the final things you’ll notice will be the car’s diagnostic light. It’ll light up on the dashboard, notifying you there’s something wrong. It may be too late for you to do anything if you’ve made it this far, though. 

Always double-check when you’re replacing your car’s transmission fluid. 

Using the correct fluid is essential to its function. You can find which one your car uses in the back of its manual. 

There should be a label somewhere in the manual that tells you which color your fluid should be. 

It’s always easier to look at the fluid’s color if you’re not sure which one to get. 

As long as that’s right, it’ll work in your car. 

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Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!