To Change, Or Not To Change Your Car’s Transmission Oil

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Transmission fluid or gear oil is ignored by many car owners because they fail to understand its importance especially in an automatic car. It is what lubricates the gearbox and also acts as a coolant to cool down the immense heat generated by the gears running at high rpm. A badly maintained gearbox has lower efficiency overall as the engine needs more energy to turn the gears against a highly viscous fluid. In automatic cars, it is the torque converter that manages to cope up with the changes in RPM. All these things reduces efficiency and also affects the mileage.

Gear fluid is more important for automatic cars and that is why they require a more frequent transmission oil change with less time intervals than what is instructed for a manual transmission. The gear oil is changed less frequently than an engine oil but it is always a good practice to keep a check on all the fluids in a car. Most transmission failures occur because of less attention given to the gearbox.

However, changing the gear oil is NOT always a good idea, and it depends on the condition of the transmission. Older cars with rarely maintained gearboxes tend to wear out the metal running on metal over a period of time. If the gear oil is not changed on time, the fluid starts accumulating tiny bits of metals that were eroded and the liquid is now contaminated. Once this happens, it is advised not to change the gear oil. Flushing your transmission fluid and replacing it with a new one will probably cause a gearbox failure because the contaminants have placed themselves at their positions and are now set. A new fluid will clean the transmission and leave gaps where the contaminants were placed, keeping everything in place. New transmission oils have detergents, who in an attempt to clean up things in the old transmission, remove the slug, etc which kept everything in place previously.

The goal is to change the oil at the right time. But what is the right time? Before small particles are seen in your gear oil and it smells burnt, it is the right time. Do not look for symptoms of a bad transmission fluid. It might already be too late. Change it as instructed by the manual issued by the company before your transmission gets damaged.


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  1. question says

    after how may km do i need to change vitz 2011 gear oil ….dont have the manual

  2. Syed Hussein El-Edroos says

    May I be permitted to disagree a little bit. All automatic transmissions have a screen and/or filter. If these become choked with impurities when the oil change is delayed, then less oil will flow to the oil pump. There will be lower pressure to change gears, lubrication will be reduced and cooling will not be as effective.

  3. Syed Hussein El-Edroos says

    I presume the Vitz has an automatic transmission.

  4. Johnny D Good says

    he means he don’t have the car’s manual

  5. Munaf Razzak says

    every 30,000 km because its CVT transmission have the same car same model it costs 5000 to 6000

  6. Auto Oil Changers says

    Interesting blog, I think most people only focus on changing their oil, we never really think about the transmission fluid.

  7. Imran Ahmed says

    On my 4×4 1328 cc Jimny I change the differential and gearbox oils every two years. On my manual corolla I changed the gearbox oil at 4 years (35,000 Km), not sure if it was necessary or not.

  8. Billy says

    Still no mention of when/ what interval to change the oil???Thanks for the useless Article and wasting our time!

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