The correct and reasonable selection of lubricating oil and grease can ensure the power of the vehicle, improve the reliability of the vehicle and prolong the service life of the vehicle. However, in practical use, there are many misunderstandings in the selection of lubricants and greases, causing serious problems. The adverse consequences.
1 Diesel vehicles use petrol motor oil
The engine oil is divided into gasoline engine oil and diesel engine oil. Although the gasoline engine and the diesel engine work under high temperature, high pressure, and high load conditions, the two are still quite different.
First, the compression ratio of a diesel engine is more than twice as large as that of a gasoline engine. The pressure on the main parts is much greater than that of a gasoline engine. Therefore, the production materials of some parts are the same. For example, the gasoline engine main bearing bush and the connecting rod bearing bush can be made of babbitt metal with softer material and good corrosion resistance, while the diesel engine bushing must use high performance materials such as lead bronze or lead alloy, but these materials have poor corrosion resistance.
For this reason, some anti-corrosion agents should be added to the diesel engine oil so that a protective film can be generated on the surface of the bearing pad to reduce the corrosion of the bearing pad and improve its wear resistance. Since gasoline engine oil does not have such anti-corrosion agent, if it is added to the diesel engine, the bearing pads will be prone to spotting, pitting, even falling into pieces, and the engine oil will soon deteriorate.
In addition, the sulfur content of diesel fuel is greater than that of gasoline. This harmful substance will form sulfuric acid or sulfurous acid during the combustion process. Together with high-temperature and high-pressure exhaust gas, it will enter the oil sump to accelerate the oxidation and deterioration of the engine oil. Therefore, diesel engine oil Antioxidants need to be added to make the oil alkaline. If there is acid gas intrusion, it can play a role in the neutralization, will not cause the oil to oxidize too quickly. The gasoline engine oil is not added with this additive, so it is neutral. If it is used in a diesel engine, it will quickly deteriorate and deteriorate due to the corrosion of the acid gas. Therefore, diesel vehicles must use diesel engine oil instead of gasoline engine oil.
2 Domestic cars use imported oil
Some people now think that the imported motor oil must be better than the domestic engine oil. Therefore, the use of imported motor oil on domestic vehicles, especially new ones, often causes many ills. For example, most imported oils have low viscosity and cannot meet the requirements of domestic vehicles for oil viscosity. In addition, the thermal expansion systems and associated clearances for domestic engine parts are larger than those of imported cars. Most domestic car engines do not have oil coolers. If imported oil is used, the oil pressure will be too low due to over-dilution of the engine oil, or even the specified working pressure will not be achieved. This will not meet the need for normal lubrication and will increase the wear of the engine.
3 blindly select the level of lubricant
Lubricating oil lubrication quality is directly related to the length of the engine life, especially the new vehicle is very strict on the lubricating oil requirements, what lubricating oil is selected, when to replace, how to replace, etc. should be carried out in accordance with the provisions of the manufacturer.
When selecting the engine oil, it is necessary to pay attention to the quality level, but also pay attention to the viscosity level. First, the performance level should be selected according to the compression ratio, displacement, etc.; then the viscosity level should be selected according to the temperature and load. Good quality oil can ensure good engine lubrication, reduce wear, extend engine life, and extend the oil change intervals. When choosing the oil viscosity, in addition to the air temperature conditions, the engine oil lubrication and sealing should be used to try to use low-viscosity engine oil in order to save fuel.
4 Mixed engine oil
All kinds of lubricating oils, their base oils are the same except for different viscosity grades. The only difference is the type and quantity of the added ingredients. Therefore, the types and quality grades of lubricants are generally classified according to the types and amounts of the added components. Lubricants with different types of additives cannot be mixed, otherwise they may cause chemical reactions in the additives of the oil and impair the proper performance of the lubricant. With the continuous improvement of additives and their formulations, some common oils such as QE/CC, QF/CD, etc. have been developed and produced, which can be used within the scope of the indicated grades. Therefore, whether or not the lubricating oil can be used in combination should be based on the requirements of the specification and comprehensively check the name, type and grade of the oil. Therefore, the use of a reasonable level of use and appropriate brands, can not be mixed.
5 The higher the viscosity of the oil, the better
In order to reduce the wear of moving parts, the lubricating oil must have sufficient viscosity to form an oil film between moving parts at various operating temperatures. However, the viscosity of the lubricating oil must not be higher than the degree that affects the start of the engine, and it requires that the friction generated under continuous operating conditions be minimal. The use of lubricating oils with excessive viscosity increases the wear of the parts due to:
(1) The viscosity of the lubricating oil is too large, the flow is slow, and although the oil pressure is high, the flow rate of the lubricating oil is small, and the lubricating oil cannot be replenished to the friction surface in time.
(2) When the viscosity of the lubricating oil is large, the frictional resistance between the friction surfaces of the moving parts increases, which affects the dynamic performance of the engine and the fuel economy.
(3) If the viscosity of the lubricant is large, the circulation speed will be slow, and the cooling and heat dissipation effect will be deteriorated, making it easy to overheat the engine.
(4) Since the circulation speed of the lubricant is slow, the number of passages through the filter is small, and it is difficult to timely remove the worn out metallic dust, carbon particles, dust and other impurities from the friction surface.
Therefore, do not use lubricating oils with excessive viscosity, and do not think that the higher the viscosity, the better. Under the condition of ensuring lubrication, according to the temperature range during use, use the lubricant with small viscosity as much as possible. However, for engines that have worn out relatively severely and have a relatively large gap, lubricants with a slightly higher viscosity can be used properly.
6 Engine oil is black
Engine oil is operated under harsh high temperature conditions and is easily oxidized and degraded to produce acidic synthetic polymer deposits, resulting in destructive lubrication.
In addition, the burning of the exhaust gas into the crankcase can also cause the oil to deteriorate. Therefore, the oil used for a certain period of time will usually deteriorate and lose its proper lubrication. However, with the continuous improvement of the quality of lubricants, especially the promotion of the use of thickened engine oil, the blackening of engine oil does not necessarily mean that the engine oil is deteriorated. . This is because the clean dispersant added to the viscosified engine oil disperses the deposits on the machine components in the oil, causing the engine oil to darken. Whether it is deteriorating or not, the testing of various indicators should be carried out, and oil quality should be changed according to the quality, so as to reduce unnecessary waste. For example, oils with a protective agent such as YY 102 will also turn black when used for a certain period of time. Therefore, black oil does not mean that the oil is deteriorating.
7 best use of multi-grade lubricants
Multi-grade lubricating oils (also known as multi-viscosity lubricating oils) have light oil properties at low temperatures and heavy oil properties at high temperatures. Where multi-grade oils are used, a multi-grade oil can replace a variety of single-grade oils. Although multi-stage oils can meet extremely cold and warm seasons and heavy-duty engine oils, cold-start diesel engines that do not have difficulties are generally recommended to use single-viscosity oils, which will help extend engine life. Therefore, do not think it is best to use multi-viscosity lubricating oils.
8 Refining lubricants rather than less
The danger of too little engine oil is well-known, so some owners are afraid of lack of oil and tile, and the amount of oil that is added is often excessive. Too many lubricants have many hazards:
(1) Crankshaft agitation causes the oil to form a large amount of foam and degenerate, increasing crankshaft rotation resistance, not only increasing engine fuel consumption, but also reducing engine power.
(2) As the oil flows along the cylinder wall to the combustion chamber, “burning oil†is caused, which increases the consumption of engine oil and deteriorates the emission.
(3) Accelerate the formation of carbon deposits in the combustion chamber, making the engine prone to deflagration.
Therefore, it is a misunderstanding that the engine oil is rather less, and the general oil level should be kept slightly below the dipstick.
9 universal joint cross shaft grease
In the general vehicle maintenance manual, it is clearly stated that calcium-based grease is used for the key shaft and intermediate bearing of the transmission shaft expansion sleeve, and the cross shaft needle roller bearing and the three-axle drive vehicle rear axle drive middle bearing use gear oil. However, in actual work, due to the lack of refuelling equipment, some repairmen mistakenly lubricate the cross-axis needle roller bearings with calcium-based greases for the sake of convenience, causing premature damage to a large number of cross-axis bearings. Since the mouth of the universal joint cross-fuelling gear oil is a very common grease nipple, it often causes a misunderstanding. In fact, the grease is not filled with needle roller bearings. Because of the large viscosity of the grease, when grease is applied to the inner cavity of the cross shaft through the grease nipple with a grease gun, the resistance of the grease into the confined inner oil passage is large. At this time, the grease pressure will push the pressure relief valve opposite the nozzle. When it overflows, the repairman mistakenly believes that the bearing has been filled with oil. Therefore, gear oil should be filled with a gear oil pressure gun.
10 Grease when installing cylinder head gasket
Some repairmen prefer to apply a layer of butter to the cylinder pad when installing the cylinder pad, which is believed to increase the engine's tightness. However, doing so is not only useless but harmful. The cylinder head gasket is an important sealing element between the engine block and the cylinder head. It not only tightly seals the high-temperature and high-pressure gas in the cylinder, but also seals the cooling water and engine oil that penetrates the cylinder head and the cylinder block. If grease is applied to the cylinder head, some of the grease will be squeezed into the cylinder water channel or oil gallery when the cylinder head bolts are tightened. Grease left on the cylinder pad is affected by high temperature, some of which will flow into the cylinder to burn off, and the other part will be burned and deposited on the joint surface of the cylinder block and the cylinder head, causing the engine to leak. Therefore, do not apply grease when installing the cylinder head gasket.
11 Apply grease to tire bolts or nuts
In order to easily tighten the nuts and prevent corrosion, many repairmen apply grease to the tire bolts and nuts. In fact, this is a wrong practice. According to the mechanical principle, the self-locking characteristics of the threads after the tightening of the nuts are the reason that the thread helix angle is smaller than the equivalent friction angle between the threads. In the bolted connection, the helix angle is a certain value, and the equivalent friction angle varies with the friction between the threads. Obviously, the equivalent friction angle between the threads after oiling is reduced, and the self-locking performance of the bolt connection is deteriorated. Therefore, do not apply grease to the bolts and nuts of the tire to prevent loosening of the tire.
12 Diluted grease by adding lubricating oil
Some repairers prefer to dilute the lubricant when it is used in winter. This practice is wrong. Because the structure of the grease is a colloidal structure composed of a thickening agent and a base oil, the thickening agent forms a structural network, and a base oil (usually an ordinary lubricating oil) is adsorbed on the network to form a stable structural system to ensure the thickening agent. And the base oil will not be separated. If the oil is added after the fat has been added, it may not be evenly dispersed and contained in the network even though it is agitated. When it is used, it is easily separated and lost, which is not conducive to lubrication. If a small-thickness grease is needed in winter, use the No. 1 or No. 2 calcium-based grease with a small number.