Shell is a Dutch brand. Royal Dutch Shell Group (Royal-Dutch-u002FShell-Group-of-Companies), also translated as "Shell", is currently the world's largest oil company headquartered in The Hague, Netherlands and London, UK. It was formed by the merger of Royal Dutch Petroleum and Shell in the UK. . The following are the functions of engine oil: 1. Friction relief: An oil film of sufficient thickness separates the surfaces of relatively sliding parts to reduce wear. 2. Sealing effect: Engine oil can form a sealing ring between the piston ring and the piston to reduce gas leakage and prevent external pollutants from entering. 3. Anti-rust effect: Lubricating oil can be adsorbed on the surface of parts to prevent water, air, acidic substances and harmful gases from coming into contact with the parts. 4. Buffering effect: When the engine cylinder mouth pressure rises sharply, the load on the piston, piston chips, connecting rod and crankshaft bearing is suddenly aggravated. This load acts as a buffer against the impact load through the transmission lubrication of the bearing. 5. Cleaning effect: Good engine oil can circulate carbides, sludge, and wear metal particles on engine parts back to the oil tank. Through the flow of lubricating oil, the dirt generated on the working surface of the parts is washed away.