SG engine oil refers to the engine oil that meets the standard certification of API quality grade SG. With the development of automobile engine and other technologies, engine oil is constantly updated to better meet the needs of engines. At present, SG engine oil has been basically eliminated, and fewer and fewer people use this grade of engine oil. The standard of qualified engine oil mainly includes the following points: 1. Lubrication: Many parts in the engine have rapid relative sliding. In order to avoid excessive wear, the oil needs to establish an oil film with sufficient thickness between the two sliding surfaces to reduce wear. 2. Auxiliary cooling: Engine oil can't play a cooling role, but it can bring the heat generated by fuel combustion in the engine back to the oil tank and help the water tank cool the engine by radiating it into the air. What really plays a cooling role is the water or antifreeze outside the engine shell. 3. Cleaning: Good engine oil can bring carbides, sludge and worn metal particles on engine parts back to the oil tank through circulation, and wash away the dirt generated on the working surface of the parts through the flow of lubricating oil. 4. Sealing and leak-proof: Engine oil can form a sealing ring between the piston ring and the piston to reduce gas leakage and prevent external pollutants from entering. 5. Rust prevention and corrosion prevention: The engine oil can be adsorbed on the surface of parts to prevent water, air, acidic substances and harmful gases from contacting parts, thus preventing corrosion and oxidation of parts. 6. Shock absorption and buffering: When the engine cylinder pressure rises sharply, the load on the piston, piston ring, connecting rod and crankshaft bearing is very heavy, and the engine oil can buffer the impact load through bearing lubrication.