Gear oil is a liquid lubricant consumed in gears for decrease of resistance and wear of the gear tooth surfaces, elimination of the heat produced by the functioning gear and corrosion safety of the gear parts. The subsequent properties of gear oils are imperative for their process: Proper viscosity; Capacity to endure extreme pressures; Thermal and oxidation constancy; Deterioration and corrosion protection; Compatibility with seal products. Gear oils should offer consistent, proficient (low friction), low cost of repairing operation of gears at altered speeds, temperatures, oil contagions. Forms Of Gear Oils Amalgamations of additives impart special functions to gear oils: Rust and corrosion pre-emptive gear oils : Rust and corrosion pre-emptive oils are mostly mineral base. They comprise rust and corrosion inhibitors. The thickness of R&C oils in accordance to the ISO grading system is 32 to 320. Compounded gear oils : Compounded oils are inorganic base. They comprise rust and oxidation inhibitors, demulsifies and up to 10% of greasy oils for better lubricity. Compounded oils are used mostly in warm gears. The thickness of compounded oils in accordance to the ISO grading system is 460 to 1000. Extreme Pressure (EP) gear oils : EP oils may be either inorganic or artificial base. They comprise EP extracts, rust and corrosion inhibitors, anti-foaming proxies and demulsifies. The thickness of EP oils in accordance to the ISO grading system is 68 to 1500