Viscosity: 75W85. MT-85 75W85 GL-4 Gear Oil. SAE Viscosity Grade (Gear Oil) 75W85. Manufacturer's Part Number: 50504. Size: 1 Quart. ABOUT RED LINE GEAR OIL FOR MANUAL TRANSMISSIONS. • Excellent gear and synchro protection, balanced slipperiness for easier shifting in cold climates.