【Owner's home car knowledge】Engine oil has always been a word that many car users are familiar with. So what is engine oil used for? What do those labels mean? What kind of engine oil is suitable for which car? And how to choose the right engine oil for your car? These are all the knowledge we need to know, today's editor will give you a detailed explanation:
● Function of engine oil:
The engine is the heart of the car. There are many metal surfaces that rub against each other in the engine. These parts move fast and the environment is poor. The working temperature can reach 400°C to 600°C. Under such harsh working conditions, only qualified lubricating oil can reduce the wear of engine parts and prolong the service life. So what requirements should qualified lubricating oil meet? That is to say, what are the six functions of lubricating oil?
1. Lubrication and wear reduction: There is rapid relative sliding between the piston and the cylinder, between the main shaft and the bearing bush. To prevent excessive wear of the parts, an oil film needs to be established between the two sliding surfaces. There is an oil film of sufficient thickness to separate the surfaces of relatively sliding parts, so as to achieve the purpose of reducing wear.
2. Cooling and cooling: The engine oil can bring heat back to the oil tank and then dissipate it into the air to help the water tank cool the engine.
3. Cleaning and cleaning: Good engine oil can circulate the carbides, sludge, and worn metal particles on the engine parts back to the oil tank, and wash away the dirt on the working surface of the parts through the flow of lubricating oil.
4. Sealing and anti-leakage: engine oil can form a sealing ring between the piston ring and the piston, reducing gas leakage and preventing external pollutants from entering.
5. Anti-rust and anti-corrosion: lubricating oil can absorb 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 pressure of the cylinder port of the engine rises sharply, the load on the piston, piston bits, connecting rod and crankshaft bearing is suddenly aggravated. This load is transmitted and lubricated by the bearing, so that the impact load it bears plays a buffering role .
● Classification of engine oil:
The engine oil currently on the market can be simply divided into two types: mineral oil and synthetic oil due to the difference in base oil (vegetable oil is not counted due to the scarcity of production). Synthetic oil is divided into: full and synthetic and semi-synthetic. Fully synthetic motor oil is the highest grade.
The biggest difference between the two lies in: synthetic oil is used at a wider temperature, has a longer service life, and is more expensive; the same oil film requirements can be achieved with synthetic oil at a lower viscosity, while mineral oil needs to be used compared to synthetic oil. Only thicker viscosity can meet this requirement. In the same working environment, synthetic oil has a much longer service life than mineral oil, so the cost is higher, but after comparing the oil change times, it is not much higher than mineral oil.
● Mark of engine oil:
The viscosity of lubricating oil is mostly marked with grades such as SAE. SAE is the abbreviation of "Society of Automotive Engineers" in English. For example: SAE15W-40, SAE5W-40, "W" means winter (winter), the smaller the number in front of it, the better the low-temperature fluidity of the engine oil, which means the lower the ambient temperature available for use, and it will affect the engine during cold start. The better the protection ability of the oil; the number behind the "W" (behind a horizontal line) is the index of the high temperature resistance of the oil, and the larger the value, the better the protection performance of the oil at high temperature.
(SAE) Applicable ambient temperature (°C)
5w resistance to external low temperature -30°C
10w resistant to external low temperature -25°C
15w resistance to external low temperature -20°C
20w resistance to external low temperature -15°C
30 Resistance to external high temperature 30°C
40 Resistant to external high temperature 40°C
50 Resistance to external high temperature 50°C
In this way, 5W-40 oils are suitable for external temperatures ranging from -30°C to 40°C; while 10W-30 oils are suitable for external temperatures ranging from -25°C to 30°C.
● Classification of engine oil:
The series starting with "S" represent gasoline engine oil, and the specifications are: SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM. The series starting with "C" represent diesel engine oil, and the specifications are: CA, CB, CC, CD, CE, CF, CF-2, CF-4, CG-4, CH-4, CI-4. When the two letters "S" and "C" exist at the same time, it means that the engine oil is of gasoline/diesel type.
From "SA" to "SL", each increment of a letter, the performance of the oil will be better than the previous one, and there will be more additives in the oil to protect the engine. The lower the letter, the higher the quality level, and the oil level of international brands is mostly above SF level.
After reading the basic knowledge of engine oil, you must have a lot of questions. Let's start to answer questions:
★Question 1: Are all cars suitable for top-level fully synthetic motor oil?
As I said so much just now, the performance of fully synthetic engine oil is indeed very good, with good fluidity, whether it is a cold start in winter or high temperature resistance in summer, it is very good, and the oil change interval is long, which can protect the engine to the greatest extent. But fully synthetic motor oil is not suitable for miniature and small cars worth tens of thousands of yuan...
Tens of thousands of economical cars, because the machining accuracy of the engine is relatively low, and the gap between the cylinder and the piston ring is not the best. This kind of engine often appears on models with low car prices and is relatively sticky High-quality engine oil is used to seal between the cylinder and the piston ring. If a thinner fully synthetic engine oil is used, there will be some small problems in the sealing of this engine, and it always feels powerless to drive. And after parking, most of the full synthetic will flow back to the oil pan, and the lubrication and sealing of the engine will be damaged. Therefore, after getting up and starting in the morning, the engine will suffer greater wear and tear. There is no such problem in the engine.
Therefore, fully synthetic motor oil is a good oil, but it is not suitable for low-cost economical car engines.
★Question 2: How to choose engine oil for supercharged engine--if you brush the computer, it is recommended to use fully synthetic engine oil
If it is an ordinary turbocharged car, it is enough to use the original engine oil, but if you flash the computer, please read the following paragraph:
Because the working speed of the turbocharger is too high, any ball bearing cannot withstand the strength of 100,000 revolutions per minute, so the main shaft is not connected with the ball bearing and the turbine body, but adopts a floating design, and the main shaft is floating in the oil Yes, the extremely narrow space between the turbine body and the main shaft is filled with flowing oil, which not only acts as a lubricant, but also takes away impurities between the main shaft and the turbine body and plays a cooling role.
This is where the problem lies. Still taking the Bora 1.8T as an example, the original 0.38bar supercharged value is generally between 100,000 and 150,000 rpm, and the original engine oil is fully sufficient to support this speed and heat dissipation. But after flashing the computer, the supercharging value will skyrocket, and the turbine speed will also skyrocket to 200,000-300,000 rpm. At this time, the first thing that can’t handle it is the original engine oil. The consistency is high and the fluidity is poor, so when the main shaft rotates at a super high speed, the engine oil cannot provide the necessary lubrication and heat dissipation. Some friends even maintain it outside, and the grade of the engine oil is not even as good as the original engine oil. There will be a problem of burning oil, that is, the aforementioned turbo is damaged.
Fully synthetic engine oil is relatively thinner, with better lubrication and heat dissipation. After the turbine speed increases, this thinner engine oil can flow 100% to the lubricating parts, so many problems mentioned above will not occur.
★Question 3: Why do German cars generally change their oil every 7,500-10,000 kilometers, while Japanese cars usually change their oil every 5,000 kilometers?
This is what I said before, the relationship between mineral oil and synthetic motor oil. The original engine oil of the general model of Japanese cars (the price of which is less than 300,000 yuan) is generally mineral oil, and the oil change cycle should not be too long. Generally, it needs to be replaced after more than 5,000 kilometers. ) Generally, semi-synthetic engine oil is used, so the oil change interval may be around 7500-10000 kilometers.
For German cars with a price of around 150,000, the original engine oil is basically semi-synthetic oil, so the natural oil change cycle will be 2,500 kilometers longer than that of Japanese cars of the same grade. The original engine oil of many German cars with a price of more than 200,000 yuan is fully synthetic, and the theory of oil change cycle can exceed 10,000 kilometers.
★Question 4: Why do some high-end cars burn oil?
High-end cars generally use fully synthetic engine oil, and even many super sports cars use the super racing oil of the 0W-50 series with excellent fluidity. Better fluidity of engine oil means thinner viscosity. There are many benefits mentioned above. Another disadvantage is that because it is thinner, the proportion of engine oil flowing into the combustion chamber from between the cylinder and the piston ring is also greater. Therefore, the oil consumption is naturally much higher than that of those family cars.
It is inevitable that high-end cars will burn some oil, unless you don't use high-end oil. However, if the consumption exceeds half a liter of engine oil per 2,000 kilometers, it is also a problem, not a normal consumption.
★Question 5: Is it okay to just change the engine oil without changing the filter?
Engine oil not only lubricates, but also plays a very important role in taking away the dirt inside the engine. These dirt are filtered out by the machine filter. If the engine oil is changed without changing the filter, the dirt cannot be completely removed, so it is equivalent to There's no point in changing the oil. You must change the filter when changing the oil, which is a dead rule.
★Question 6: Is the engine oil always black after replacement?
Engine oil mainly lubricates various parts inside the engine, especially the lubrication of the piston and cylinder wall. Here, the product of combustion is a dark jelly, so the engine oil has changed color since it was injected into the engine on the first day of use. up. However, the normal used engine oil should be dark brown. If it is really pure black, it is also problematic. It is likely that the oil change interval is too long.
★Question 7: Can different brands of oil be mixed?
Each brand of engine oil additives is different, mixing them may cause deterioration of the chemical components, and mixing them is seriously not recommended.
★Question 8: For car owners all over the country, what should they pay attention to when using engine oil?
In the Northeast, Xinjiang, and Tibet regions, it is recommended to use relatively sparse anti-low temperature 5W series engine oil. In extremely cold areas such as the Arctic and Antarctic Circles, engine oil may even use 0W series engine oil.
In North China, East China, and South China, it is recommended to use normal 5W-30/40 or 10W-30/40 engine oil;
In extremely hot areas like Hainan, it is recommended to use 40 or 50 engine oil, and high temperature resistance is a must;
● Conclusion:
The use of engine oil is very interesting, but don’t think it is too complicated. If you are not sure, just use the original engine oil provided by the 4S shop or the brand’s professional repair factory to ensure that your engine has no problems.
If you need to provide special protection for the engine or modify the engine, it is recommended that you immediately change to a higher-grade engine oil. You can rest assured that the original engine oil matches the characteristics of the original engine and is not suitable for the modified engine.
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