Transmission oil is a specialized lubricant engineered for the complex rotating and stationary components within automatic and manual transmissions. It provides critical lubrication, hydraulic pressure for actuator operation, and frictional control for clutch pack engagement. Formulations vary significantly by transmission type, requiring adherence to specific OEM specifications regarding viscosity, friction modifiers, and material compatibility. Key performance characteristics include thermal stability, shear resistance, and oxidation control to maintain consistent performance under high stress and temperature. Modern formulations often incorporate synthetic base oils and advanced additive packages for extended service intervals and improved efficiency.