Lubrication Properties

Gear oil and transmission fluid are both lubricants that are used to protect the moving components of your vehicle's transmission system. However, they differ in their lubrication properties. Gear oil is designed to provide heavy-duty protection to the gears, while transmission fluid is designed to provide smooth shifting and protect the transmission's internal components.

Chemical Composition

The chemical composition of gear oil and transmission fluid is different, and this affects their performance. Gear oil typically contains high levels of sulfur and phosphorus, which make it more effective at protecting gears from wear and tear. Transmission fluid, on the other hand, contains friction modifiers, which help to reduce the wear on the transmission's clutch plates.

Viscosity Rating

Gear oil and transmission fluid also differ in their viscosity ratings. Gear oil has a higher viscosity rating than transmission fluid, which means that it is thicker and can provide better protection to the gears under heavy loads. Transmission fluid has a lower viscosity rating, which allows it to flow more easily and provide smooth shifting.


Gear oil is typically used in manual transmissions, differentials, and transfer cases. It is also used in heavy-duty vehicles and off-road vehicles that require additional protection for their gears. Transmission fluid, on the other hand, is used in automatic transmissions, and it is essential for the proper operation of the transmission system.


Both gear oil and transmission fluid require regular maintenance to ensure that they are performing at their best. Gear oil should be changed every 30,000 to 50,000 miles, while transmission fluid should be changed every 30,000 to 60,000 miles, depending on the manufacturer's recommendations.