Gear Oil Vs. Transmission Oil: In-Depth Comparison 2023

Gear oil is generally for use in manual gearboxes and transmission oil for automatic transmissions. They are not like automotive lubricants; they are different in the case of rules. But what’s the difference between gear oil vs. transmission fluid? To fully understand both fluids, we must look first at the vital difference between the transmission and gearbox.

The work of gearbox and transmission are the same as they allow gear changes to control force, speed, and direction of travel. But the most important thing is that they achieve all this differently. That’s why, to function correctly, they need different types of fluid.

Gear Oil Vs. Transmission Oil

Manual Gearbox

Manual gears work based on a system of two shafts with gears. The gearbox generates heat, force, and friction when two moving objects collide.

Gear Oil Properties:

For example, your gear oil must make these gear transitions smooth. Besides this, gear oil must be able to prevent damage to your elements as they shift. Also, gear oil has to be following properties:

High Viscosity

Gear oil’s main property is its viscosity which you notice for the first time. This oil is much thicker than engine oil. The average motor oil viscosity is 5w30, and the gear oil is 75w90.

High viscosity ensures that the full-gear train is completely lubricated. Most importantly, when gear oils come together, they are well cushioned from shock damage.

Heat Resistance

The operation of a manual gearbox creates a lot of friction and a lot of heat. Gear oil can withstand high temperatures, transferring heat from the gear train.

Able To Work Under Extreme Pressure

Gear oil has extreme pressure additives to tolerate high pressures generated during driving, especially where hypoid gears are involved. Additionally, they help keep the oil stable and work consistently.

Automatic Transmission:

Automatic transmissions work on a planetary system and function depending on engine demand. Mechanical gears are smaller and have many more moving parts than a manual gearbox.

Transmission Oil Properties:

As such, the required lubrication is at a different level than a manual gearbox. Transmission fluid has to be able to transfer power from the oil pump to the clutch. It’s because it controls the movement of gears. That’s why transmission fluid has to be following properties:

Low Viscosity

Transmission fluid is thin hydraulic oil. To effectively lubricate the system’s delicate parts, the oil viscosity is kept low – usually around 0W5 or 5W10. Most importantly, this oil must flow freely to transfer power from the engine to the transmission. Mainly dextron type oils are commonly used as auto transmission oil.

Heat Resistance

Accordingly, transmission fluid acts as a coolant similar to gear oil. And it transfers heat away from the mechanism because of high pressure and friction. But it has a lower boiling point than gear oil. Consequently, this oil needs additives to improve its life.

Anti Foaming

You should keep air away from the oil because it will interfere with to transfer of the force from oil to transmission. That’s why transmission fluid has anti-foaming properties that can tolerate this.

Gear Oil Vs. Transmission Fluid

Many web pages emphasize transmission oil, and others recommend gear oil. In that order, the choice comes down to the actual product application. While some manual gearboxes use transmission oil instead of gear oil, you can’t use gear oil in automatic transmissions.

This is because gear oil is too viscous for these systems and causes clogging between elements. In the case of automotive oils, the golden rule is that always use recommended oil in your transmission.

If you are going to perform maintenance work on your vehicle, check your owner’s manual for details on what is safe to put in your system. When you want maintenance on your vehicle, check your manual for details on what’s safe to put.

Gearbox Oil Types:

Gearbox oil is a lubricant to decrease wear and friction between moving gears. Different gearbox oil types are determined by the temperatures built by the different speeds of running the gears. The three types of gearbox oil are:

Rust-Prevention Gear Oils

Rust-inhibiting gear oils are mineral-base and petroleum-base compounds that have rust inhibitors. These gearbox oils come in two categories, monograde and multigrade gear oils. Monograde gear oils come for use at certain “normal” temperatures.

In contrast, multigrade gear oils are best in cold or warm temperatures and average temperatures. The rust-inhibiting gear oil’s advantage is that it can increase the gear life. Even so, it allows gear to operate properly at high temperatures. You can use this gearbox oil in low-load gearboxes.

Extreme Pressure Gear Oils

Extreme pressure gear oils are formulated as synthetic or mineral based. These are known as EP gear Oil such as EP 460 or EP 220 Gear Oil. EP gearbox oil types are multigrade and contain anti-rust and anti-foaming additives. Moreover, these additives prevent the gear oil from thickening and losing its cooling capacity.

Generally, EP gearbox oil life is limited due to all additives. This gearbox oil is best used for gearboxes that operate under high pressure. Gears wear quickly due to excessive stress on the gears. Without that, EP gear oil can increase the life of these high-load-bearing gearboxes.

Synthetic Gear Oils

Synthetic gear oils are chemically based gearbox oils made from ester oils, polyalphaolefins (PAO), or polyglycols. In addition, these gear oils are multigrade, each with preventative additives as part of their makeup. This gearbox oil can work at extremely high or low temperatures.

In particular, it can prevent foaming, rusting, and gear wear inside the gearbox. You can use these oils in gearboxes that operate in unusual conditions like sub-zero and humid climates.

Additional Information About Transmission Oil:

There is some additional information about transmission oil. Have a look:

Heavy-Duty Truck Transmission Oil:

Heavy-duty transmission oil is best for manual transmissions that tolerate heavy-duty and enlarged drain intervals. Additionally, this oil comes with advanced additives and synthetic base stock. They will give a fantastic performance in cold temperatures. Furthermore, they can protect your truck from corrosion, oxidation, and deposits.

Thus, they can provide incredible cold-temperature performance and protect your vehicle from oxidation, corrosion, and deposits. They are suitable for heavy-duty trucking, on-highway, buses, vans, commercial lights, etc.

Dexron Type Transmission Oil:

Dexron is a trademark used for an automatic transmission fluids (ATF) series manufactured in GM transmissions. The original Dexron (VI) transmission oil was launched in 1967.

Over the years, the original Dexron(B) has been replaced by Dexron-II(C), Dexron-II(D), Dexron-II(E), Dexron-III(F), Dexron-III(G) ), Dexron-III(H), Dexron-VI(J), etc.

Read : Dexron 2 Vs 3

Read: Dexron 3 Vs Dexron 6

In terms of increasing demand, GM has upgraded Dexron specifications over the years. That means new oils are only sometimes consistent with previous fluids and transmissions.

How Often Do I Need My Semi Truck Transmission Oil Change?

Oil change and battery service are the most frequent maintenance of your truck. Depending on your usage, you should change your battery every six months.

You should change your transmission oil in semi-trucks at least every 30,000 to 60,000 miles or once every two years. ATF is like engine oil – you need to change it periodically along with the filter to keep your truck running properly.

Read More about Semi Truck Transmission oil change

Consult your vehicle’s owner’s manual to know the correct mileage intervals recommended by the manufacturer. Drivers always know better about their trucks. We recommend that you schedule ahead of time to drive your semi-truck without oil.

FAQ(Frequently Asked Questions):

Q. What is transmission oil used for?

Transmission fluid lubricates a vehicle’s transmission elements for optimal performance. In cars with automatic transmissions, this oil also works like a coolant. There are different types of auto transmission fluid. The kind used in individual trucks and vehicles depend on the transmission type inside.

Q. What are the different types of gearbox lubricants?

Gear lubricants can generally be categorized into compounded, R&O, and antiscuff. But which gear oil will be best for your vehicle, can determine your owner’s manual of the car.

Q. What does 80w90 gear oil mean?

The value of “W” (W=winter suitability) implies the oil’s flowability at cold temperatures. Transmission oil with 80W flows down to -26°C. This gear oil is best for Central European winter. The number “90” refers to the gear oil kinematic viscosity at 100 degrees Celsius.

Q. Is axle oil and gear oil the same?

No, you can’t use both oils interchangeably. Axles, final drives, differentials, and other gear sets used in mobile component applications need particular lubricants.

Q. What is the best gear oil for manual transmission?

Standard recommended manual transmission oil includes 75w90, 80w90, SAE 80W, and SAE 90. Sometimes, it suggests the automatic transmission fluid and multigrade engine oil. Nonetheless, manual transmission oil is generally best suited for manual transmissions.

The Final Verdict

Though you can use transmission fluid inside the gearbox, this is impossible for automatic transmissions. Notably, gear oil is too thick for a transmission system that it can jam the whole function. In a bad situation, it’s best to use maintenance tips or contact a mechanic.

Selecting the best oil from gear oil vs. transmission oil, which is suggested for your automobile. In this way, you can keep your car’s durability. So, right now, choose the proper oil for your vehicle.

Read Also: Gear Oil Vs Engine Oil


Emon is Lubricants specialist who studied on Petroleum Engineering in UAE. He have more than 10 years experience on different kinds of lubrication including automobile troubleshooting.