The function of engine oil is 1. Lubrication and wear reduction: there is rapid relative sliding between piston and cylinder, and between spindle and bearing bush. In order to prevent the parts from wearing too fast, it is necessary to establish an oil film between the two sliding surfaces. There is an oil film with sufficient thickness to separate the surfaces of relatively sliding parts, so as to achieve the purpose of reducing wear. 2. Cooling: Engine oil can bring heat back to the oil tank and then radiate it into the air to help the water tank cool the engine. 3. Cleaning: Good engine oil can circulate carbides, sludge and worn metal particles on engine parts back to the oil tank, 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 protection: Lubricating oil can be adsorbed on the surface of parts to prevent water, air, acidic substances and harmful gases from contacting with parts. 6. Shock absorption and buffering: When the engine cylinder pressure rises sharply, the load on the piston, piston plate, connecting rod and crankshaft bearing suddenly increases, and this load is lubricated through the bearing, so that the impact load it bears plays a buffering role.
The oil grade is divided into two standards. The first is the engine oil quality rating standard formulated by API gravity (API). S stands for gasoline engine oil. L stands for grade. The higher the letters API SA, SB, SC, SE, SF, SG, SH, SJ, SL and SM, the higher the grade of engine oil. SL is the highest quality engine oil in the world at present. C stands for diesel oil. F stands for grade, from API CA, CB, CC, CD, CE, CF, CF-4, CG-4 and CH-4, the lower the letter, the higher the grade of oil. The second is the SAE standard, also known as the standard for measuring oil viscosity, which is divided into single viscosity and compound year. For example: SAE 15W-40, SAE5W-40, "w" stands for winter. The smaller the number in front of it, the better the low-temperature fluidity of engine oil, which means that the lower the available ambient temperature, the better the engine protection ability during cold start. The number after "W" (one horizontal) is the index of high temperature resistance of oil, and the larger the number, the higher the temperature of oil.
1, the selection principle is to select the appropriate quality grade first, and then select the required viscosity grade. The selection of quality grade is based on the severity of internal combustion engine working conditions, oil quantity and compression ratio, fuel properties and so on.
2. When choosing the performance level, we should consider the use environment comprehensively and use it flexibly. When choosing the quality grade of diesel engine oil, it can be determined according to the reinforcement coefficient of the engine. However, when the sulfur content of diesel oil is greater than 1.0%, a higher grade oil should be selected.
3. Higher grade engine oil should be selected, although the price is slightly higher, but the comprehensive economy is better, such as prolonging the oil change period, saving oil consumption, reducing friction and wear, prolonging the service life of parts and reducing maintenance costs.