1. Viscosity representation:

The viscosity of lubricating oil is mostly marked by SAE and other grades. SAE is the abbreviation of "Society of Automotive Engineers" in English. For example, SAE40, SAE50 or SAE15W-40, SAE5W-40, "W" means winter. The smaller the number in front of it, the thinner the viscosity of the oil and the better the fluidity, which means the lower the ambient temperature that can be used. The better the protection ability of the engine during cold start; the number after "W" (behind the - horizontal line) is an indicator of the high temperature resistance of the engine oil. The larger the number, the better the protective performance of the engine oil at high temperatures. Higher viscosity engine oil also has relatively higher resistance to the motion system, which not only consumes power and increases fuel consumption, but the oil is also prone to oxidation, affecting cold start protection. Oils with only one set of values, such as SAE40 and SAE50, are single-grade engine oils and cannot be used in cold winter. Like SAE15W-40 and SAE 5W-40, there are two sets of values. 15 means that the viscosity of the engine oil is No. 15 in winter, and 40 means that the viscosity of the engine oil in summer is equivalent to No. 40 engine oil. This means that this kind of engine oil is an advanced "multi-grade engine oil", suitable for a wide range of areas from low temperature to high temperature. The viscosity value will change with the temperature to give the engine comprehensive protection.

(SAE) Applicable ambient temperature (°C)

5w　-30°C (my understanding: it refers to minus 30 degrees Celsius, which means it can start normally at minus 30 degrees Celsius) . )

10w　-25°C

15w　-20°C

20w　-15°C

30°C< /p>

40 40°C

50 50°C

Advantages of multi-grade oil:

1. Use all year round to extend engine life , reduce wear (reduce wear caused by cold start);

2. Improve fuel economy;

3. Reduce lubricating oil consumption;

4. Reduce Wear;

5. Provide good low-temperature lubricity;

6. Longer oil change period;

7. Recommended by most heavy-duty engine manufacturers .

The existing engine oils in the market are classified according to the SAE method. Single-grade engine oils: there are 6 types of winter oils and 4 types of summer oils. Multi-grade engine oils: 16 types of winter and summer general-purpose oils.

The winter oil grades are: 0W, 5W, 10W, 15W, 20W, 25W;

The summer oil grades are: 20, 30, 40, 50;

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The general oil brands for winter and summer are: 5W-20, 5W-30, 5W-40, 5W-50, 10W-20, 10W-30, 10W-40, 10W-50, 15W-20, 15W- 30, 15W-40, 15W-50, 20W-20, 20W-30, 20W-40, 20W-50.

2. Indication of quality:

SL/SJ: Indicates use in gasoline engine vehicles

CF/CG: Indicates use in diesel engine vehicles

< p>The details are as follows: API is the abbreviation of the American Petroleum Institute, and the API grade represents the grade of engine oil quality. It uses simple codes to describe the engine oil's ability to do its job.

API engine oil is divided into two categories: the series starting with "S" represents gasoline engine oil; the series starting with "C" represents diesel engine oil; when the two letters "S" and "C" exist at the same time, It means that this engine oil is universal for gasoline and diesel engines.

The meaning of the letters after S or C is; from "SA" to "SL", with each increasing letter, the performance of the engine oil will be better than the previous one, and there will be more in the engine oil. Additives used to protect engines. The further back the letters are, the higher the quality level. Among international brands, most engine oil grades are SF or above. For example, Shell Helix Plus is API SL grade, while Shell Helix Red Motor Oil is API SG grade. This means that the quality level of Helix Extra is higher than Helix Red. .

3. Basic classification of engine oils:

The engine oils currently on the market can be simply divided into mineral oil and synthetic oil due to their different base oils (vegetable oils are not included due to their rare production. ). The highest grade oils are synthetic oils.

The biggest difference between the two is that synthetic oil can be used at a wider range of temperatures, 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 can achieve the same oil film requirements. It is necessary to use a thicker viscosity relative to synthetic oil to achieve this requirement. In the same working environment, synthetic oil has a much longer service life than mineral oil, so its cost is higher. However, after comparing the number of oil changes, it is not much higher than mineral oil.

IV. What kind of engine oil to use for EFI cars

More and more of the new cars are EFI cars, and many car owners are proud to own EFI cars. . Indeed, EFI vehicles have many advantages. For example, its engine power is increased by 15%-20% on average compared to carburetor engines. However, its requirements for engine oil, especially technical indicators such as high oxidation resistance, are becoming more and more stringent.

Electronic injection engines equipped with three-way catalytic converter devices have even stricter requirements for engine oil. Two conditions must be met to install a three-way catalytic converter. First, the gasoline must be lead-free, because the lead in the gasoline will poison the catalyst and render it ineffective; second, the EFI vehicle equipped with a three-way catalytic converter must use a phosphorus content of Engine oil below 0.12%. If the phosphorus content in the engine oil is too high, it will cause the catalyst to fail, shorten the life of the three-way catalytic converter, and exhaust gas emissions will not be minimized. The phosphorus content in engine oil must be less than 0.12% to ensure the normal operation of the three-way catalytic converter. Engine oils with phosphorus content below 0.12% are classified as APISH and above. Therefore, if your car is an EFI car and is equipped with a three-way catalytic converter, you should choose engine oil of SH and above when adding engine oil, so as to ensure that your car drives smoothly and safely.

5. Specific selection of engine oil

●Differentiated by viscosity

Viscosity refers to the internal friction of a fluid (including gas and liquid) when it flows , that is, flow stagnation resistance. Examples: 1. It affects the starting of the engine when the car is cold. This will be more obvious at low temperatures. For example, when you go to snow-capped mountains to enjoy the snow in winter, 2OW-50 will be harder to start than 5W-40. 2. Increase fuel consumption. Oil with high viscosity also has high resistance, which will cause higher friction resistance in the operation of the internal parts of the engine, thus increasing fuel consumption. 3. Increase engine wear during startup. When the engine has not been started for a period of time, the oil originally attached to the upper part will flow back to the oil pan. The upper part lacks enough oil to keep the engine in starting condition. If the oil viscosity is thick, the flow will be slow, so the chance of wear will increase. . 4. If the viscosity of the engine oil is too thick, the internal resistance will be large, and the resistance will be converted into heat, causing the temperature of the machine parts to rise during operation.

●Depends on the temperature of the operating environment

Almost any automobile manufacturer will recommend the most appropriate engine oil viscosity in the owner's manual. The car manufacturer that is the most picky about engine oil in the world is undoubtedly Porsche. Because it is an air-cooled engine, everything is cooled only by engine oil. In its internal technical bulletin, every engine oil is submitted for inspection (required by the oil manufacturer). Make a conclusion. But the most basic thing is that it still requires car owners to decide what kind of engine oil to use based on the temperature of the environment. For Shanxi, the lowest temperature is no less than 25 degrees Celsius, and the highest temperature is no higher than 40 degrees Celsius. Within this range, 5W-40 and 10W-40 are generally more suitable. The above is the common sense you must know when choosing engine oil. First use the temperature of the car environment to determine the viscosity of the engine oil, and then consider mineral oil or synthetic oil based on your budget.

●What kind of oil should be used for pure transportation?

If the car is just a transportation tool and you only use it when commuting to and from get off work, 10W-40 general mineral oil is enough. You used it. If you want to save money on gas, fully synthetic 5W-40 can meet your requirements because it flows quickly and reduces wear and tear on your engine when you start it. A quick aside: 4S uses 10W-40 for QQ, but I don’t know whether it’s mineral oil or synthetic?

●What kind of oil should you use if you like the engine speed?

The higher the engine speed, the higher the relative temperature will be, so you should use oil with a higher viscosity. Such as 5W-50, 10W-50 or 15W-50.

But as mentioned earlier, the higher the viscosity, the greater the relative resistance, and the engine performance will be somewhat weakened, so synthetic oil can make up for this shortcoming. Because synthetic oil can use a lower viscosity to meet the working conditions that must be met with a high viscosity compared to mineral oil. But at this time, you have to consider the engine volume output of the vehicle itself. For example, a four-cylinder vehicle with less than two liters will reach the red line as soon as the rpm is pulled. Perhaps a slightly thicker engine oil (for example, 10W-40 compared to 5W-40) will be more suitable. Because the gap between the cylinder and the piston ring is sealed by engine oil, the sealing effect of high viscosity is of course better. For vehicles with more than three liters and more than six cylinders, the engine speed of this type of car usually does not reach the red line (of course there are exception), so there is less need to pay attention to it. Another way to determine the viscosity is to listen to the sound of the engine valve after running for a while. If the "dada" sound is obvious, then you should increase the viscosity.

●What kind of oil should be used in high compression ratio engines?

Synthetic oil with high viscosity is the only choice. Such as 5W-50, 10W-50 or 15W-50. If you also often pull the rpm to the red line, you can consider 10W-60.

6. Discuss the oil change interval

According to general terms, the oil change interval of vehicle oil is 5,000 kilometers. Many car owner friends regard this as a fixed understanding. In fact, each vehicle has different engine conditions, oil used, and operating environment, and its reasonable oil change intervals should also be different to a certain extent, and cannot be generalized.

1. Engine condition

Please clean the inside of the engine of a new car. There is little carbon deposit and other impurities, so the oil change interval can be extended appropriately. But it should not exceed 7,500 kilometers. No matter how good the engine oil is, its chemical properties will change after a certain mileage, especially the additives in it will gradually lose their effectiveness and will no longer protect the engine. Old engines, especially engines that lack maintenance, have a lot of carbon deposits inside. After new oil is added, it is easy to be contaminated, causing discoloration and qualitative changes. Therefore, the oil change interval should be shortened appropriately. Of course, if possible, it is best to thoroughly clean the inside of the engine.

2． Oil used

There are two standards for identifying engine oil: quality grade (API) and viscosity (SAE). Quality levels generally range from SC, SD to SM. The higher the level, the better the quality. Modern cars, especially sedans, mostly have high-speed engines and have higher oil requirements. Generally speaking, engine oils above SF grade have good oxidation resistance, anti-wear properties, clean dispersion and viscosity stability under high temperature and high shear. They can provide reliable protection for the engine and the quality stability will not change for a long time. Under normal circumstances, it can fully meet the oil change interval of 5,000 kilometers. Some car owners, mostly taxi owners, use SD or even SC grade engine oil in order to save money, which makes it inappropriate to follow the 5,000-kilometer oil change requirement. Because low-grade engine oil has poor stability under harsh working conditions, deteriorates quickly, and is prone to carbon deposits. From the perspective of caring for the vehicle, if this type of engine oil is used, the oil change interval should be shortened to 3,000 kilometers or even less. It is best to use the engine oil recommended in the vehicle manual, otherwise you may not save money due to the shortened oil change interval.

8. Influence of the use environment

The environment also has a certain impact on engine oil. High temperature, extreme cold and dusty environments can easily accelerate the deterioration of engine oil. Car owners should not only choose engine oil of appropriate grade and viscosity for the environment, but also shorten the oil change cycle appropriately. The specific requirements depend on the situation. Generally, it is appropriate to shorten the cycle by 1/5-1/3.

Many car owners have a vague understanding of the use of engine oil, thinking that as long as it is engine oil, it can be changed every 5,000 kilometers. As everyone knows, if the type of engine oil is not properly selected and the oil change interval is not properly grasped, long-term use will have a great impact on the vehicle. Some models of the same model are still in good condition after driving for 20,000 to 300,000 kilometers. In addition to driving methods, the rational use of engine oil is also very important. As long as you can sum up experience, make careful comparisons, choose engine oil scientifically and master the oil change intervals, your car will stay young!