Full Synthetic MT-85 75W85 GL-4 Gear Oil, 1 Quart. MT-85 75W85 GL-4 GEAR OIL. PART NUMBER: 50504. SAE Viscosity Grade (Gear Oil) 75W85. RED LINE MT-85 HIGH-PERFORMANCE GEAR OIL is a full-synthetic ester-based lubricant designed for use in manual transmissions and front-wheel-drive transaxles.