Engine Oil vs Transmission Oil | Can They Be Used Interchangeably?

Yes, they belong to the same clan of lubricants. Wait, does that make you assume that they perform the same functions? Well, the answer to this question is a big NO! There is a distinction between engine oils and transmission oils. And, that too a significant one. Actually, more than one!

Both engine oil and transmission oil serve the purpose of lubricating the automobile for a smooth and proper functioning and efficiency. Though they come from the family of lubricants at large, but, both engine oil and transmission oil stand out and can be differentiated from each other in numerous ways.

In this article which is more or less an engine oil vs transmission oil battlefield, we aim at discussing a few points which distinguish engine oil and transmission from each other.

Majorly, Transmission Oil/Fluid supports the vehicle’s automatic transmission, while the Engine Oil empowers its engine. On one side, engine oil serves the purpose of enhancing the lifespan and quality of the engine by lubricating it properly. On other hand, transmission oil acts as a power transmitter in the face of a lubricant for the valves and clutches.

It wouldn’t be wrong to say that if the engine oil is a vehicle’s basic food then the transmission also competes at an equal level while acting as a vehicle’s immunity booster.

Further, in this article, we aim at jotting more points highlighting engine oil vs transmission oil. Not only about how they differ in looks and appearance, you will also get to read what happens if you use these lubricants interchangeably. Scroll ahead!


Engine oil vs Transmission oil: Lifespans

Mileage and time have differing effects on the transmission fluid and engine oil.

  • Engine Oil Mileage 

With time and miles, engine oil loses its usefulness. You’ll need to change your engine oil every 3000-6000 miles, depending on the kind. If you wait too long, it will lose its quality, causing your engine to break down.

  • Transmission Fluid Mileage

Transmission fluid, unlike engine oil, does not need frequent replacement. Between 30,000 and 60,000 miles, manual transmission fluid may need to be replaced, as such can engine oil get into automatic transmission lasts much longer. Around 60,000-10,0000 miles, they are routinely replaced.

Transmission fluid levels dropping in a short period is unusual, therefore if you observe low transmission fluid levels often, get it examined for a transmission fluid leak.


Engine oil vs Transmission oil: Appearances   

While both transmission fluid and engine oil are oils, they are different from each other not only in terms of their function but also in appearance and consistency.

  • Engine Oil Appearance

Engine Oil Appearance

Few qualities of the engine oil are as follows.

  1. It has an amber tone to it and is transparent.
  2. It often has a lower viscosity than small amount of motor oil in transmission, allowing it to flow more freely between engine components.
  3. As engine oil ages, it darkens. Expired oil has a murky appearance with suspended particles. When seen with a dipstick or in the oil pan, it also seems to have changed viscosity.


  • Transmission Fluid Appearance

Transmission Fluid Appearance

Few qualities of the transmission fluid are as follows.

  1. It comes in a variety of colors, from green to dark crimson.
  2. The color of automatic transmission fluid is generally red.
  3. Dark green manual transmission fluid (also known as gear oil) is common.
  4. CVT fluid is a transparent and green specialized fluid used in Continuously Variable Transmission (CVT).


Also Read:-

Engine Oil vs Motor Oil – Is There Any Differnce


Choosing Transmission Oil for Manual Gearbox

Manual gears work based on a two-shaft system with gears that mesh following human input through the clutch and gear stick. This implies that when the two moving items collide, the manual gearbox generates a lot of heat, force, and friction.

As a consequence, gear oil must be able to make these gear changes as smooth as possible in order to minimize damage to the components as they shift. It is important to choose your gear oil wisely. Here is a  list of a few gear oil features to look out for. 

  • High Viscosity

The viscosity of gear oil is the first thing you’ll notice. It’s substantially thicker than motor oil, which is typically 5W/30, while gear oil is often 75/90.

The high viscosity guarantees that the whole gear train is adequately lubricated and, more critically, that the gears are well cushioned as they come together.

  • Resistance to Heat

The operation of a manual gearbox generates a great deal of friction and, as a result, a great deal of heat. Gear oil can tolerate high temperatures and transport heat away from the gear train while not boiling off or decreasing too quickly to be used for a long time.

  • Able to Function Under Extreme Pressure

Extreme pressure additives are commonly used in gear lubricants to help them resist the high pressures created during vehicle operation, especially when hypoid gears are used. They aid in maintaining the oil’s stability and consistency of operation.


Choosing Transmission Oil for Automatic Transmission

Automatic gearboxes work on a planetary system, with gears switching automatically based on the engine’s needs. In comparison to a manual gearbox, automated gearboxes have smaller gears and many more working elements.

As a result, the degree of lubrication needed differs from that of a manual gearbox. Not only must the transmission fluid provide enough lubrication, but it must also be capable of transferring power from the oil pump to the clutches that govern gear movement. To do this, the transmission fluid must possess the following characteristics:

  • Low Viscosity

Transmission fluid is simply hydraulic oil that has been thinned down. The viscosity of the oil is maintained low to properly lubricate the sensitive portions of the system – often about 0W/5 or 5W/10. Most essential, to convey power from the engine to the gearbox, it must be somewhat free-flowing. The issue that transmission fluid faces in maintaining lubrication while maintaining constant clutch engagement.

  • Keep the Channels Between Components Clean

To ensure that build-up in the channels is maintained under control, detergent is added to the transmission fluid.

  • Resistance to Heat

Transmission fluid works as a coolant in the same manner as gear oil does, transferring heat away from the mechanisms created by friction and high pressure. However, since its boiling point is lower than gear oil, it needs additives to extend its life.

  • Anti-foaming

It’s critical to keep air out of the fluid since it would obstruct the passage of force from the liquid to the transmission. To assist fight this, transmission fluid includes anti-foaming qualities.


Putting Engine Oil In Transmission: How Will This Impact?

All said and done, but have you ever thought what will happen if you, even by mistake, replace your transmission oil with engine oil? Relatable? 

If you mistakenly add engine oil to your gearbox, it should do little to no harm in most circumstances. Simply cleanse the system and remove the oil as quickly as possible.

However, if you overfill your automatic can engine oil get into transmission and leave it alone, you may experience the following symptoms:

  • There’s a grinding sound coming from your gears.
  • When in gear, it’s difficult to operate.
  • While driving, the gears are slipping.
  • Your transmission emits a burning odor.
  • The “Check Engine” light has been turned on.
  • The gearbox makes a lot of noise.

What Is The Best Way To Check The Transmission Fluid Level?

Because most current automobiles lack a gearbox dipstick, expert service maintenance is required. The right approach should be described in your car’s user handbook.

If your automobile does have a transmission dipstick, here’s how to check the fluid level in your gearbox:

  • Make sure your automobile is parked on a level surface. Any hot engine components should be avoided.
  • While the engine is on or off, the car handbook will instruct you on how to inspect your gearbox.
  • Determine the location of the transmission fluid dipstick. Pull it out with care and wipe it clean with a clean towel.
  • Replacing the dipstick in the transmission fluid is necessary. To check the fluid level, remove the gearbox dipstick once again.
  • The transmission fluid level on the transmission fluid dipstick should be between the L and H markings. A fluid leak in your transmission might be indicated by low transmission fluid. Refill with the right quantity in this scenario.
  • Reinstall the transmission fluid dipstick after repairing the fluid leak.


Engine oil and transmission oil serve quite distinct roles, despite their similarities. Engine oil improves the fuel economy and general performance of the engine, while transmission fluid delivers power to the hydraulic elements and transmission of the vehicle.

Both of these fluids, however, perform best when they are maintained on a regular basis.

Engine oil should be changed on a regular basis, while gear oil (MTF and ATF fluid) should be maintained according to the manufacturer’s recommendations.