Changing the transmission fluid (gear oil) is a necessary maintenance operation, but scientific specifications must be followed to avoid damaging the transmission system. Manual transmission fluid is typically changed every 40,000 to 60,000 kilometres, while automatic transmission fluid is recommended to be changed every 60,000 to 80,000 kilometres. The specific interval should refer to the vehicle manual, as adjustments may be required based on different brands and operating conditions (such as frequent heavy loads or high-temperature environments). When replacing, it is essential to strictly match the API grade and SAE viscosity grade specified by the manufacturer; inferior fluids will accelerate gear wear and compromise hydraulic system performance. Operationally, It is best to perform the change when the vehicle is cold: first, completely drain the old fluid and clean the oil pan, then refill with new fluid using either the gravity method (lower cost but leaves more residual old fluid) or the flush machine method (more thorough fluid replacement but at higher cost). After completion, a test drive should be conducted to verify smooth gear shifting. If the fluid appears black, cloudy, or contains metal particles, it should be replaced immediately. However, do not blindly follow non-OEM recommendations for shortened change intervals.
