Top > Glossary > About ATF・CVTF


AT/CVT fluid (ATF/CVTF) has three functions: 1. Operating control devices hydraulically (functioning as hydraulic fluid), 2. Transmitting power as a fluid coupling (functioning as medium fluid), 3. Lubricating moving parts (functioning as lubricant). For the requirements of ATF/CVTF, see the table below.

Requirements of ATF

AT receives engine power via a torque converter and changes gears in the planetary gear unit hydraulically according to running conditions.

●Viscometric properties: Ensuring lubrication against severe temperature change at a high viscosity index
●Frictional properties: Stable coefficient of friction to change gears smoothly
●Durability of judder prevention: Preventing unpleasant vibration due to the slip lock-up system
●Antifoaming: Preventing deterioration of hydraulic power due to foaming

Requirements of CVTF (for push belt CVT)

CVT receives engine power via a torque converter and changes the pulley diameter (gear ratio) hydraulically and without steps according to running condition.

●Frictional properties : Maintaining a high coefficient of friction to transmit power
●Durability of judder prevention : Preventing unpleasant vibration due to the lock-up clutch
●Shear Stability : Preventing the viscosity of fluid from decreasing against high shearing force。

【Recommendation for changing ATF/CVTF regularly】

A burned clutch plate

An element clogged with wear particles.

Bottom of the oil pan covered with sludge

Most failure of AT/CVT is caused by fluid deterioration. If you keep driving with deteriorated fluid, important structures of your car will be damaged and in the worst case, your car will not be able to run or a reckless accident will be caused.

【Fluid deterioration】

New fluid (Red) 1. Deteriorated fluid 2. Foaming 3. Fluid mixed with wear particles 4. Fluid mixed with water
The color of new fluid is clear red. Used in tough condition for a long time, or used for a long time without fluid being replaced. Fluid becomes foamed. Power transmission becomes inefficient due to minute bubbles, and poor mileage results. Wear particles or sludge from the clutch or gears is mixed with the fluid. Water from a cooler line is mixed with the fluid. The fluid becomes opaque due to emulsification.

【Symptoms due to fluid deterioration】

It is recommended that fluid be changed before the symptoms below appear (every two years/within 20,000 km).