Differential fluid, also called gear oil, is a heavy-duty lubricant specifically formulated to protect the high-pressure gears, bearings, and moving parts inside your vehicle's differential. It ensures wheels spin at different speeds during turns while preventing grinding and overheating.Key Types and SpecificationsTo find the exact fluid your vehicle requires, consult your owner's manual. The fluid can differ significantly depending on your car's drivetrain:Viscosity Rating: Common weights include 75W-90, 80W-90, and heavy-duty 75W-140 for towing or heavy hauling.API