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Automotive Transmission Fluid Types

Automatic transmission fluid is distinctly different from transmission fluid made for manual transmissions. In the US, most passenger cars have an automatic transmission, which means the transmission changes gears as required automatically - the driver does not need to take any action. Manual transmissions, on the other hand, are dependent on the operation of the clutch and shifter by the driver each time a gear shift is required. Transmissions require distinct fluids for best performance depending on the vehicle make, model and year.


Manual transmission fluid (MTF) – protection and operation

Key performance and protection requirements for manual transmissions include synchronizer compatibility, durability and shift quality. The transmission synchronizer must engage smoothly for proper shift performance. Additionally, anti-wear and load carrying components in the transmission fluid must ensure long synchronizer life and gear protection. Manual transmission fluid, like engine oil, is generally brown to amber in color.

Transmission gears and parts

Commonly recommended manual transmission fluid formulations include SAE 80W, 75W-90, 80W-90 and SAE 90. In some cases, a multi-grade engine oil or automatic transmission fluid may be recommended. However, a manual transmission fluid is typically the most optimal for manual transmissions. Always refer to the owner’s manual for the proper transmission fluid to use in your vehicle.


Automatic transmission Fluid – protection and operation

Automatic transmission fluid, commonly referred to as ATF, ensures proper operation, performance and protection of the automatic transmission. This fluid is generally red in color with the exception of the fluid made specifically for Continuously Variable Transmissions (CVTs).

Cross section of a modern automatic transmission of a truck

Critical areas of ATF performance include:

  • Heat resistance and thermal stability to help prevent deposit and sludge from forming due to high temperatures
  • Frictional characteristics to enable smooth gear changes by supplying the correct friction to the transmission clutches and bands
  • Extreme pressure/load carrying performance to ensure anti-wear and gear durability
  • Viscosity stability or proper fluid thickness over a wide temperature range
  • Low temperature flow to ensure effective operation of hydraulics and electronics controls at low temperature


Continuously Variable Transmissions (CVTs)

CVTs have continuously changing speed ratios unlike typical automatic transmissions which have distinct gear shifts. CVTs can also help improve fuel economy. Hybrid vehicles are commonly equipped with CVTs and they are occasionally used in non-hybrids. A CVT-specific fluid should always be used to ensure proper performance and protection. There is no standard color for CVT fluid, however Castrol Transmax CVT Fluid is red.


What kind of transmission fluid does my car take?

The type of transmission fluid you should use depends upon the make, model and year of your vehicle. For example, many General Motor cars will require a DEXRON fluid and Ford cars commonly specify a MERCON fluid. Always follow the vehicle manufacturer recommendation for proper fluid use and change interval. In many cases, fluid change intervals will be more frequent if the vehicle is operated under severe conditions. Such conditions will be defined by the manufacturer. 


What are the signs of low transmission fluid?

Low fluid levels can result in noise, clutch slippage, overheating of clutch components and harsh shifting. It is important to follow manufacturers guidelines and have your transmission serviced at the recommended intervals.


Checking Transmission Fluid

The level of most transmission fluids can be checked with the cap and dipstick under the hood. Refer to your owner’s manual for the proper way to check transmission fluid level.