Can Old and New Transmission Oil Be Mixed?

[Miller]

Old and new transmission oil should not be mixed. Here are the consequences of mixing old and new oil: 1. Reduced oil pressure: This causes the oil in the transmission to thicken, leading to hindered internal heat dissipation and excessively high oil temperatures, thereby shortening the lifespan of the transmission and drivetrain components. 2. Slippage phenomenon: If the transmission oil is not replaced, the vehicle may experience weak acceleration when starting, resulting in frequent slippage during driving. 3. Accelerated wear: Prolonged failure to replace the transmission oil can lead to oil degradation and evaporation under high-speed and high-temperature conditions, causing rapid wear of components and damage to internal transmission parts.