Phillips 66® Transmission Oil SAE 90 is a high-quality, straight-grade mineral lubricant specifically engineered for use in heavy-duty manual transmissions, transfer cases, and final drives that require a non-EP (Extreme Pressure) oil. This specialized formulation is designed for gearboxes where sulfur-phosphorus additives—commonly found in standard gear oils—could lead to chemical corrosion of yellow-metal components. By utilizing premium, high-viscosity-index mineral base stocks, it provides a robust lubricating film that maintains its integrity under heavy loads and high operating temperatures. It is the ideal choice for legacy commercial vehicles and industrial equipment where a simple, reliable API GL-1 lubricant is specified to ensure mechanical longevity and internal cleanliness.