In the summer heat, not only the human body will have various adverse reactions, but also the car. Today, I will share with you one of the things you need to pay attention to in summer-lubricants.
The role of lubricating oil
The heat generated by the friction between the various moving bearing surfaces of the engine is second only to the heat when the engine cylinder is burned, and the lubricating oil takes the heat away by pressure lubrication, thus ensuring the normal operation of the friction surface. The heated lubricating oil returns to the oil pan through the oil passage for cooling. In terms of the structure of the engine, the oil pan is located under the engine*, and it is exposed to the air. It is generally made of materials with good thermal conductivity, and the lubricating oil is air-cooled through it. The cooled lubricating oil is sent to the lubricated surface again. The viscosity of the lubricating oil is very important for protecting the engine. Only when the lubricating oil has sufficient viscosity, can it be ensured that the oil film can be maintained between the engine parts at various temperatures, thereby protecting the normal operation of the engine.
Why pay attention to the viscosity of lubricating oil in high temperature in summer?
First of all, when the engine is running at high temperatures, the anti-oxidation stability of the lubricating oil deteriorates, which intensifies its thermal decomposition, oxidation and polymerization. At the same time, the dust in the dry air and the moisture in the humid air enter the engine oil pan through the air intake system and the crankcase vent to contaminate the lubricating oil, so the lubricating oil is prone to deterioration.
Second, the viscosity of lubricating oil changes with the increase of temperature, that is, the viscosity of lubricating oil decreases when it is heated, which easily causes excessive consumption of lubricating oil.
Third, when the engine is running at high temperature, the thermal expansion of metal parts is large, the normal fitting clearance between the parts becomes smaller, and the abrasion is intensified. At the same time, the engine running at high temperature adheres carbon deposits and colloids on the piston crown, combustion chamber wall, valve head and other parts, which makes the thermal properties of metal parts worse and accelerates the damage of the mechanical parts. In addition, due to the overheating of the engine, the oil becomes thinner, the oil pressure is reduced, and the lubricating oil film is not easy to form, which also accelerates the wear of the parts.
Reasonably choose lubricating oil viscosity
Lubricants are usually classified according to viscosity and quality. There are 6 types of oils in winter, 4 types of oils in summer, and 16 types of general-purpose oils in winter and summer. Summer lubricating oil grades are 20, 30, 40, and 50. The larger the number, the higher the viscosity and the higher the applicable temperature. For example: SAE15W-40, SAE5W-40. The number after “W” indicates the index of the high temperature resistance of the lubricant. The larger the value, the better the protection performance of the lubricant at high temperature. In general, consumers in most parts of the country from April to September can choose summer lubricants No. 15W-40 or No. 10W-40.
At the same time, for high-end cars, it is recommended to choose high-quality fully synthetic lubricants as much as possible. Compared with general mineral oil, synthetic oil has little change in viscosity with temperature, and it can still maintain a proper viscosity at high temperatures.
Lubricating oil is not that the higher the viscosity, the better
Although the viscosity of lubricating oil is very important, car owners should abandon the misconception that “the higher the viscosity, the better”, and choose the appropriate quality level according to the actual vehicle conditions, temperature and engine conditions. Only in the case of a large gap between the parts of the automobile engine, the lubricating oil with a large viscosity should be selected.
Using lubricating oil with excessive viscosity will have at least two disadvantages:
First of all, when the viscosity is higher than the degree that affects the engine start, it is likely to cause serious wear when the engine starts. Because the lubricating oil is too viscous and flows slowly, although the oil pressure is high, the throughput of the lubricating oil is not much, and it cannot be added to the friction surface in time. The oil circulation speed also slows down, and its cooling and heat dissipation effects will become poor, which will cause the engine to overheat. Due to the slow circulation of lubricating oil, the number of passes through the lubricating oil filter is reduced. Therefore, it is difficult to clean the worn-out metal chips, carbon particles, and dust from the friction surface in time.
Another disadvantage of using lubricating oil that is too viscous is energy consumption. Because the viscosity is too high, the friction between the friction surfaces of the parts increases. To overcome the increased friction, more fuel is consumed, resulting in a huge waste of energy. It is understood that low-viscosity lubricants have become an international trend in foreign countries. In China, although there are no compulsory requirements for energy-saving lubricants, low viscosity will be the future development trend.
Summary: In the high temperature in summer, the choice of lubricating oil is also a matter of great care. It is necessary to choose lubricating oil with higher viscosity, but also to abandon the misconception that “the higher the viscosity, the better”. If the choice is not good, the engine will be damaged in severe cases.
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Link to this article：Introduction to the correct choice of lubricating oil in summer
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