What are the requirements for lubricants to meet? What is the role of lubricants?
Lubrication and anti-friction: Rapid relative sliding between the piston and the cylinder, between the spindle and the bearing shell. To prevent excessive wear of the parts, it is necessary to establish an oil film between the two sliding surfaces. The oil film with a sufficient thickness will slide relatively. The surfaces of the parts are separated to reduce wear.
Cooling and cooling: Oil can bring heat back to the oil tank and then distribute it to the air to help the tank cool the engine.
Cleaning and Cleaning: A good engine oil can recycle the carbides, sludge, and worn metal particles on the engine parts to the oil tank, and flush the dirt generated on the working surface of the parts through the flow of the lubricant.
Seal leakproof: The oil can form a seal ring between the piston ring and the piston, reducing the leakage of gas and preventing the entry of contaminants from the outside.
Anti-corrosion and anti-corrosion: Lubricating oil can suck on the surface of parts to prevent contact of water, air, acid substances and harmful gases with parts.
Shock absorption and cushioning: When the engine cylinder port pressure rises sharply, it suddenly intensifies the load on the piston, piston swarf, connecting rod and crankshaft bearing. This load is transmitted through the bearings and lubricates, so that the impact load can be used as a buffer.
Oil classification
At present, the oil on the market can be simply classified as mineral oil and synthetic oil because of the difference in base oil (vegetable oil is not considered due to the scarcity of production volume). Synthetic oil is divided into: full and semi-synthetic. The total synthetic motor oil is the highest Graded.
The biggest difference between the two is that
Synthetic oils use a wider temperature, longer life, and higher cost; the same oil film requirements, synthetic oil can be achieved with a lower viscosity, and mineral oil requires a relatively thicker viscosity than synthetic oil can To meet this requirement. In the same working environment, synthetic oils have a much longer lifetime than mineral oils, so the cost is higher, but after the number of oil changes, it is not much higher than mineral oil.
Oil marking
Viscosity of lubricants are often graded using SAE etc. SAE is the abbreviation of the English Society of Automotive Engineers. For example: SAE15W-40, SAE5W-40, 'W' for winter, the smaller the number in front of the engine oil The better the low-temperature fluidity, the lower the ambient temperature representing the available environment, the better the protection of the engine during a cold start; the number behind the 'W' (a horizontal back) is an indicator of the high temperature resistance of the engine oil. The larger the oil, the better the protection of the oil at high temperatures.
(SAE) Applicable Ambient Temperature (°C)
5w resistant to external low temperature -30°C
10w resistant to external low temperature -25°C
15w resistant to external low temperature -20°C
20w resistant to external low temperature -15°C
30 resistant to external high temperature 30°C
40 resistant to external high temperature 40°C
50 resistant to external high temperature 50°C
From this point of view, the applicable external temperature range of the 5W-40 oil is from -30°C to 40°C; and the external temperature range of the 10W-30 oil is -25°C to 30°C.
