Gear oil is a type of lubricant specifically designed for use in manual transmissions, differentials, and other gear systems in vehicles and machinery. It provides lubrication and protection to gears, bearings, and other components, reducing friction and wear, and helping to ensure smooth operation. Gear oils come in different viscosities and grades, and the type used depends on factors such as the type of gear system, operating conditions, and manufacturer's specifications. Some gear oils are also formulated with special additives to provide additional protection against wear, corrosion, and high temperatures.