Transmission Fluid Change: Gravity Method or Flush Machine?
2 Answers
From an economic perspective, the gravity method is more cost-effective for transmission fluid changes. Gravity fluid changes are typically cheaper than flush machine changes. Differences between the two methods: The gravity method is relatively simple to perform. Most automatic transmissions have a fluid level port that can be used for draining, checking fluid levels, or changing fluid. However, the fluid in an automatic transmission cannot be completely drained by gravity alone. The flush machine method consumes significantly more fluid per change and has a relatively more complex procedure. The gravity method can only replace 50% to 60% of the old fluid, as the remaining fluid in the torque converter and oil cooler cannot be removed. The flush machine method allows for more thorough fluid replacement. Transmission fluid change intervals: Different vehicle models have different change intervals. For manual transmissions, it's generally recommended to change the fluid every three years or approximately 100,000 kilometers; for automatic transmissions, every two years or about 40,000 kilometers; and for continuously variable transmissions (CVT), every two years or around 60,000 kilometers.
I've handled maintenance for multiple vehicles, and the method of changing transmission fluid is quite particular. The gravity method involves removing the drain plug to let the old fluid flow out by gravity, then adding new fluid. The entire process is simple and quick, usually taking just a few dozen minutes, with costs limited to the price of new fluid—around a hundred yuan. However, it only replaces about half of the old fluid, and residual contaminants may affect the transmission's lifespan, especially in high-mileage or frequently congested driving conditions. The flush method, on the other hand, uses a specialized machine to circulate new fluid, flushing out nearly 90% or more of the old fluid, resulting in a cleaner replacement that better protects internal transmission components and reduces the risk of failure. The downside is the need for specialized equipment, with costs two to three times higher and a longer duration. For automatic transmissions, high-end vehicles, or frequently used cars, I recommend the flush method. For regular manual transmission family cars, periodic gravity changes are sufficient. It's advisable to change the fluid every 40,000–60,000 kilometers, referring to the vehicle's manual—don’t neglect preventive maintenance.
