An automobile is composed of tens of thousands of parts. The matching accuracy between engine parts is very high. Friction is inevitably generated during the work of the parts, and automobile lubricating oil can reduce friction, cool down, clean and seal. , Anti-rust, anti-corrosion, shock-absorbing buffer and other functions. The importance of engine oil to the engine is no different from the human body and blood. How many miles to change the oil in the car? What is the difference between oil and lubricating oil? Which engine oil brand is better? What kind of oil is good? This special topic will explain the knowledge of lubricating oil to you.
What is automotive lubricants
Automotive lubricants are liquid or semi-solid lubricants used in various types of vehicles to reduce friction and protect machinery and processed parts, mainly for lubrication, auxiliary cooling, rust prevention, Cleaning, sealing and buffering functions. The engine is the heart of the car. There are many metal surfaces in the engine that are rubbing against each other. These parts move at high speed and in poor environment, and the operating 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.
Classification of automotive lubricating oils Mineral oils
The motor oils currently on the market can be simply divided into two types: mineral oils and synthetic oils due to their different base oils. Synthetic oils are further divided into: full and semi-synthetic. Fully synthetic motor oil is the highest grade. Compared with synthetic oil, mineral oil has weak base oil strength and needs to use larger viscosity than synthetic oil to meet the lubrication requirements under high load.
Fully synthetic motor oil
Generally speaking, the mineral base oil is replaced by esters or polyolefins, and then blended with additives, which is synthetic motor oil. Generally, the word “synthetic” will be marked on the synthetic oil drum. Synthetic engine oil has the characteristics of good stability and good durability, so generally speaking, the oil change interval of the engine using fully synthetic engine oil can be extended to 7500-10000 kilometers.
Semi-synthetic motor oil
Semi-synthetic motor oil is a lubricating oil prepared from three types of international base oils. It is a product purified by hydrofission technology on the basis of mineral oil. Synthetic motor oil is mixed in a ratio of 4:6. The purity of semi-synthetic oil is very close to that of full synthetic oil, but its cost is slightly higher than that of mineral oil. It is an ideal transition product from mineral oil to synthetic oil.
The role of automobile lubricating oil
1. Lubrication and anti-friction
When the engine is running, if some friction parts are not properly lubricated, dryness will occur. friction. Practice has proved that the heat generated by dry friction in a short period of time is enough to melt the metal, causing damage to the parts or even getting stuck (many water or oil leaking cars have failures such as pulling the cylinder and holding the axle, the main reason is this). Therefore, the friction parts in the engine must be well lubricated. When the lubricating oil flows to the friction part, it will adhere to the friction surface to form an oil film to reduce the resistance between the friction parts, and the strength and toughness of the oil film are the key to its lubricating effect.
2. Cooling down
Only a small part of the heat generated by the combustion of fuel in the engine is used for power output and frictional resistance consumption and auxiliary mechanisms In addition to being discharged into the atmosphere with the exhaust gas, most of the remaining heat will be taken away by the cooling medium in the engine. The excess heat in the engine must be removed from the body, otherwise the engine will burn out due to overheating. This is done by the engine cooling system on the one hand, and on the other hand, by the lubricating oil that absorbs heat from the surfaces of the cylinder, piston, crankshaft, etc., and then brings it to the oil pan for dissipation.
3. Washing and cleaning
During the operation of the engine, a lot of dirt will be produced. Such as the sand and dust brought by inhaling the air, the carbon deposits formed after the combustion of the mixture, the jelly formed after the oxidation of the lubricating oil, the friction between the parts and the metal filings, etc. These dirt will adhere to the friction surface of the parts, if not cleaned, it will increase the wear of the parts. In addition, a large amount of gum will cause the piston ring to stick and stick, resulting in the engine not running normally. Therefore, these dirts must be cleaned up in time, and this cleaning process is accomplished by circulating lubricating oil in the body.
4. Seal and prevent leakage
There is a certain gap between the cylinder and the piston, the piston ring and the ring groove, and the valve and the valve seat of the engine, so that the Ensure that there is no jamming between the motion pairs. However, these gaps can cause poor cylinder sealing, and the result of combustion chamber leakage is to reduce cylinder pressure and engine output. The oil film formed by the lubricating oil in these gaps ensures the tightness of the cylinder, maintains the cylinder pressure and the output power of the engine, and prevents the exhaust gas from escaping downward into the crankcase.
5. Anti-rust and anti-corrosion
When the engine is running or stored, the moisture in the atmosphere, lubricating oil, fuel oil and the acid gas produced by combustion, It will cause corrosion and rust to the parts, thereby increasing the damage to the friction surface. The oil film formed by the lubricating oil on the surface of the parts can avoid the direct contact between the parts and water and acid gas, and prevent corrosion and rust.
6. Shock Absorber
At the end of the compression stroke, the mixture starts to burn and the cylinder pressure rises sharply. At this time, the lubricating oil in the bearing clearance will alleviate the impact load on the piston, piston pin, connecting rod, crankshaft and other parts, so that the engine can work smoothly, and prevent the metal from directly contacting, reducing wear and tear.
Automobile oil grade distinction
SAE viscosity grade
The viscosity of lubricating oil is mostly marked by SAE grade, SAE is the English “American Society of Automotive Engineers” “abbreviation of. 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 oil, which means the lower the ambient temperature available for use. The better the protection ability of the oil is; the number after the “W” (behind a horizontal line) is the index of the high temperature resistance of the oil. The larger the value, the better the protection performance of the oil under high temperature.
API quality grade
The quality of lubricating oil is usually marked by API grade. API is the abbreviation of “American Petroleum Institute” in English. The series starting with “S” represents gasoline engine oil, and the specifications are: SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN. 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 oil is a gasoline/diesel universal type. From “SA” all the way to “SN”, with each increment of 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 further back the letter is, the higher the quality level, and the oil level in international brands is mostly above SF level.
The difference between engine oil and lubricating oil
1. Engine oil: is the engine lubricating oil, which can lubricate the engine and reduce wear, assist in cooling and cooling, seal against leakage, prevent rust and corrosion , shock absorption and other functions.
2. Lubricating oil: It is a liquid or semi-solid lubricant used in various types of automobiles and mechanical equipment to reduce friction and protect machinery and processed parts. Cooling, rust prevention, cleaning, sealing and buffering, etc.
3. Comparative analysis: The scope of the two is different. Oil is a kind of lubricating oil, but lubricating oil is not necessarily oil. Butter is also lubricating oil, but not oil. Lubricating oil is an oil-based liquid used to reduce friction on machinery and equipment or friction pairs. Such as gear oil, anti-wear hydraulic oil, etc. Engine oil is a common name for engine lubricating oil. Oil is just one type of lubricating oil. Like the relationship between a motor vehicle and a car.
How to choose the type of car oil
Synthetic oil has good stability, good fluidity, long oil change interval, and can protect the engine to the greatest extent, so it is basically suitable for most models. However, because the price of fully synthetic engine oil is generally higher, some small cars with less engine load in the industry prefer semi-synthetic or mineral oil for economic reasons. In addition, the grade of oil products can only be improved but not lowered. For example, it is stipulated that semi-synthetic oil can be replaced with synthetic oil, and it is stipulated that synthetic oil cannot be replaced with semi-synthetic oil.
Mileage
If you are more concerned about price and have a lot of mileage, you need to change your oil more often. Mineral oil and some synthetic oil are fine, but if you drive very little, change the oil only once a year. , It is recommended to use a better, fully synthetic oil. As for the viscosity grade, for example, some European and Japanese manufacturers have recommended the use of low-viscosity oil such as 5W-20 for environmental protection and fuel-saving considerations in recent years. You only need to follow the manufacturer’s recommendation.
Viscosity
First of all, it is recommended that you use the specifications recommended by the vehicle manufacturer, but note that the viscosity guideline of the organic oil of the vehicle manufacturer is only for the consideration of an average value. You can choose the engine oil with reference to the vehicle environment. For example, the environment is colder than most places or the engine load is higher than most vehicles, the smaller the number in front of W, and the larger the value of the small bar (such as SAE 5W-30 is recommended, and 0W can be considered in colder environments) -30 or consider 5W-40 in a hotter environment).
Age of the car
For old cars that have been driven for more than 10 years and have a mileage of more than 200,000 or even 300,000 kilometers, you can consider using high-viscosity oils such as 15W-40 and 15W-50. The advantage is that the sealing will be better, it is easier to maintain the oil pressure, and the oil consumption will be reduced. Most of this oil is mineral oil. If the old car uses low-to-medium-viscosity oil, it may cause insufficient oil pressure to meet the lubrication needs of the engine, aggravate wear, and be harmful and unhelpful.
Brand and Price
Of course, brand and value have always been important attributes of a product. The lubricating oil market is mixed, and it is generally difficult to distinguish the quality of engine oil based on appearance alone, and the principles of “you get what you pay for” and “brand represent quality” are also applicable to engine oil. But note that the choice of oil can not be blindly seeking good, expensive, suitable, oneself can bear is the best. Of course, for base oils, synthetic ones are definitely better than mineral ones.
How often to change the car oil and use the original engine oil
After buying a new car, the front is maintained in the 4S shop, and the engine oil used for maintenance is also the so-called original engine oil. In this case, you just need to change the oil at the cycle indicated in the car maintenance manual, but within the required period, change it as soon as you can.
Self-purchased oil
If the maintenance is to replace the oil purchased by yourself, the replacement cycle should be distinguished according to the different types of oil. The replacement cycle of mineral oil is half a year or 5,000 kilometers, semi-synthetic oil is half a year or 7,500 kilometers, and full synthetic oil is half a year or 10,000 kilometers.
Irregular driving (traffic jams)
Both the maintenance manual and the self-purchased oil refer to the replacement cycle under “normal driving” conditions, ie, frequent motorway driving and rarely stop-and-go. If there are frequent traffic jams, it is recommended to shorten the oil replacement mileage by 20-30%, that is, 3500-4000 kilometers for ordinary minerals, 5500-6000 kilometers for semi-synthetic oil, and 7500-8000 kilometers for fully synthetic oil.
Harsh Environments
Harsh driving conditions will also affect the oil change cycle and need to be replaced in advance. Such as driving on dust and gravel sections, the influx of a large amount of sand and dust will aggravate the blockage of the oil filter and the impurity content of the oil. For another example, it is recommended to shorten the oil change mileage by 20-30% when crossing climatic zones due to long-distance driving, or driving in areas where the temperature is lower than -20 °C.
Misunderstandings in the use of automobile lubricants Domestic cars blindly use imported high-end engine oils
Most of the imported engine oils have low viscosity, which cannot meet the requirements of domestic vehicles for engine oil viscosity. At the same time, the thermal expansion coefficient and matching clearance of various matching parts of domestic engines are larger than those of imported cars. Most domestic car engines are not equipped with oil radiators. Blind use of imported oil will cause the oil pressure to be low and even fail to reach the specified working pressure. , increasing the wear of the engine.
The lubricating oil is often added without changing.
It is correct to check the lubricating oil frequently, but only replenishing the lubricating oil without replacing it can only make up for the lack of oil quantity, but cannot completely compensate the loss of lubricating oil performance. During the use of lubricating oil, the quality will gradually decline due to pollution, oxidation and other reasons, and there will be some consumption at the same time, reducing the quantity.
It’s time to change the oil when the oil turns black
This understanding is not comprehensive. For the lubricating oil without adding a static dispersing agent, the blackening of the color is indeed a sign that the oil has been seriously deteriorated, but the lubricating oil used in modern automobiles is generally added with a static dispersing agent. This kind of lubricating oil with added tranquilizer tends to turn black after using for a period of time, but the oil at this time is not completely deteriorated.
Add as much lubricating oil as you can.
The amount of lubricating oil should be controlled between the upper and lower tick marks of the oil dipstick. Because too much lubricating oil enters the combustion chamber and burns to form carbon deposits. These deposits will increase the tendency to knock, and at the same time easily cause pre-ignition in the cylinder, and even accelerate the contamination of the lubricating oil. Secondly, too much lubricating oil increases the stirring resistance of the crankshaft connecting rod, which increases the fuel consumption.
Additives are useful
A truly high-quality lubricating oil is a finished product with a variety of engine protection functions. The formula already contains a variety of additives, and the lubricating oil pays the most attention to the balance of the formula to ensure the full play of various performances. Adding other additives by yourself not only cannot bring additional protection to the vehicle, but it is easy to react with the chemical substances in the oil, resulting in a decrease in the comprehensive performance of the oil.
Mixing engine oil at will
Different grades of engine oil have different physical and chemical properties, that is, the chemical composition, viscosity, acid value, additives and other indicators are different, and the performance of the oil will obviously change after mixing. It will cause poor lubrication effect, accelerate the wear of parts, aging of seals, and cause problems such as oil leakage.
Feel free to use substitute oil
The quality of substitute oil is directly related to the power of the engine, the fuel consumption and the degree of wear, and even endangers the service life of the engine. When substitute oil has to be used, it must be replaced with oil of the same viscosity grade, good quality and wider temperature range. Once an alternative oil is used, the operation of the engine lubrication system should be checked frequently.
Frequently Asked Questions about Motor Oils
Question 1: Are top-level fully synthetic motor oils suitable for all cars? : Fully synthetic motor oil is a good oil, but it is not suitable for low-cost economical car engines, that is, it is not suitable for micro and small cars with tens of thousands of yuan. Because the machining accuracy of these models is relatively low, the sealing of the gap between the cylinder and the piston ring needs to be more viscous oil to seal the gap between the cylinder and the piston ring.
Question 2: How to choose oil for a supercharged engine? : If you use an ordinary turbocharged car, it is enough to use the original oil, but if you brush the computer, it is recommended to use a fully synthetic oil, which is relatively thin and has better lubrication and heat dissipation. After the turbo speed is increased, this A thinner oil can flow 100% to the lubricated part.
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? : Generally Japanese car models (<300,000), the original factory oil is generally mineral oil, and the oil change interval is more than 5,000 kilometers. Mid-to-high-end Japanese cars (>300,000) generally use semi-synthetic oil. The oil cycle will be around 7500-10000 kilometers. About 150,000 German cars basically use semi-synthetic oil, while many German cars with >200,000 original oil are fully synthetic, and the oil change cycle theory can exceed 10,000 kilometers.
Question 4: Why do high-end cars burn a little oil? : High-end cars generally use fully synthetic engine oil. The better the fluidity of the engine oil, the thinner the viscosity, and the greater the proportion of the engine oil flowing into the combustion chamber from the cylinder and the piston ring, so the oil consumption is naturally It is a lot higher than those family cars, which is inevitable. However, if the consumption exceeds half a liter of oil every 2000 kilometers, there is a problem.
Question 5: Is it okay to just change the oil without changing the filter? : 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 you change the oil without changing the machine filter, the dirt will be impossible It is completely removed, so it is meaningless to change the oil. Changing the oil must change the filter, this is a dead rule.
Question 6: Is the oil all black after changing? : The product of oil combustion is a dark gelatinous substance, so the oil has been discolored since the first day it was injected into the engine. However, the normal oil should be dark brown. If it is completely pure black, there is also a problem. It is likely that the oil change interval is too long.
Question 7: Can different brands of motor oil be mixed? : Each brand of engine oil additives is different. Mixing them may cause deterioration of chemical components. Mixing them is not recommended. In addition, do not mix oil at will. The properties of oil with different indicators are different. After mixing in twos, the performance of the oil will obviously change, resulting in adverse consequences.
Question 8: Car owners across the country, what’s the point of using oil? : In Northeast, Xinjiang, and Tibet regions, it is recommended to use 5W series oil with low temperature resistance. In extremely cold regions such as the Arctic and Antarctic circles, the engine oil will even use 0W series. It is recommended to use normal 5W-30/40 or 10W-30/40 oil in North China, East China and South China; it is recommended to use 40 or 50 oil in extremely hot areas such as Hainan, and high temperature resistance is necessary.
A high-quality lubricating oil can lubricate the engine and prolong the service life of the engine. Only high-quality, adequate lubricants can carry us anywhere we can think of, travel, or work. The question of how to choose automobile lubricants and oil cannot be underestimated. Car owners can choose the oil that is suitable for their car according to their specific conditions.
