Transmission Fluid vs Motor Oil

Transmission fluid and motor oil are essential fluids for all engines; transmission fluid is for the steering system while motor oil is for the engine. However, their functions though similar in certain aspects are very different in others.
The function of motor oil is to enhance sealing, keep the engine cool, protect against rust and corrosion, keep the engine parts free of sludge, and to lubricate the moving parts of the engine. On the other hand, the main function of transmission fluid is to impart power to the automatic transmission. Transmission fluid also has the following functions:

  • Enhances sealing
  • Cools the transmission
  • Provides good heat transfer
  • Enhances hydraulic functions
  • Provides fire and radiation resistance
  • Lubricates gears, friction discs, bands, and the entire hydraulic system to prevent rust corrosion
  • Removes contaminants from gears, friction discs, bands, and the entire hydraulic system

Transmission fluid is much more specialized than motor oil. It has many performance enhancing additives as well as other additives for improved functionality. Some of these additives include:

  • Friction modifiers
  • Cold-flow improvers
  • Anti-wear additives
  • Gasket conditioners
  • Pour point depressant
  • High-temperature thickeners
  • Viscosity improvers and modifiers
  • Surfactants, detergents, and dispersants

One of the major differences of both fluids is that motor oil caters to the area of the engine that deals with combustion while transmission fluid does not. Transmission fluid is used in a closed system and so it does not need to be drained and cleaned as often as motor oil.