Little knowledge about car engine oil

Little knowledge about car engine oil

Motor oil is also called lubricating oil. If the engine is compared to the heart of the car, then the engine oil is the blood of the car. Its functions are as follows:

1. Lubrication and anti-friction: When the car is started, there is rapid relative friction between the piston and the cylinder, between the main shaft and the bearing bush, the timing gear, etc. A major function of the engine oil is to pass through the parts The friction will form an oil film between the two friction surfaces. The oil film will separate the surfaces of the two friction parts, thereby reducing wear.

2. Cleaning: Another function of engine oil is to bring carbon deposits, sludge, metal wear particles and other dirt on engine parts back to the oil pan through circulating flow to achieve a cleaning effect. .

3. Sealing and leakage prevention: Engine oil can also form an oil film between parts with relative motion to improve their sealing and help prevent air or oil leakage.

4. Anti-rust and anti-corrosion: The movement of engine oil through the parts will form an oil film on the surface of the parts. This oil film can be adsorbed on the surface of the parts to prevent water, air, etc. from contacting the surface of the parts and causing corrosion of the parts. rust.

5. Cooling: Engine oil can bring part of the heat in the engine back to the oil tank and then dissipate it into the air, helping the coolant to cool the engine.

6. Shock absorption and buffering: When the engine starts, the cylinder port pressure rises sharply, suddenly increasing the load on the piston, piston pin connecting rod and crankshaft bearing. This load is transmitted and lubricated by the bearing, absorbing the impact and Reduce vibration and act as a buffer.

What types of engine oils are there?

The engine oils currently on the market can be simply divided into two types: mineral oil and synthetic oil, according to the base oil. It can be divided into semi-synthetic engine oil and fully synthetic engine oil.

The biggest difference between mineral engine oil and synthetic engine oil 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. Mineral oil requires a thicker viscosity than synthetic oil to meet such requirements. 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.

What do engine oil labels mean?

You may have seen SAE, API, SM, 5W-40 and other labels on the packaging of engine oil, so what do these labels mean? What does it mean? Let’s explain it to you below.

The meaning of the SAE mark:

Let’s first talk about the meaning of the SAE mark. SAE is the abbreviation of the English “Society of Automotive Engineers”. The mark after SAE indicates the viscosity of the engine oil. Value, for example: SAE5W-40, where "W" represents WINTER, and the number in front of "W" represents the flow viscosity at low temperature. The smaller the value, the better the low-temperature fluidity of the engine oil. When the vehicle is cold started, it is The better the protection ability of the engine; the number after "W" is the viscosity of the engine oil at 100°C. The higher the number, the higher the viscosity.

The choice of what kind of engine oil is most suitable depends on the vehicle itself and the environment in which it is located. We have also collected the SAE viscosity grade of engine oil for your reference.

The meaning of the API label:

After talking about the meaning of the SAE label, let’s talk about what the API label means. API is the abbreviation of "American Petroleum Institute" in English. The number after API indicates the quality level of the engine oil.

API engine oil is divided into three categories:

1. The series starting with "S" represents gasoline engine oil, and the specifications are: API SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN.

2. The series starting with “C” represents diesel engine oil, the specifications are: API CA, CB, CC, CD, CE, CF, CF-2, CF-4, CG-4, CH- 4. CI-4.

3. When the two letters "S" and "C" exist at the same time, it means that the engine oil is universal for gasoline and diesel.

The meaning of the letters after S or C is: from "SA" to "SN", with each additional letter, the environmental protection level of the engine oil will be better than the previous one. The further the letter is, the more environmentally friendly it is. The higher the grade, most of the engine oil grades in international brands are SF grade or above. Currently, the engine oil with the highest environmental protection grade is "SN" grade.

Question 1: How to judge genuine and fake engine oil?

There are many types of engine oil on the market, and the purchase channels are also diverse, so many profiteers often pass off inferior products in order to make money. Low-grade mineral engine oil is sold to consumers as semi-synthetic engine oil or fully synthetic engine oil. There have been many experiences on how to tell the authenticity of engine oil, but nowadays the means of counterfeiting are very high. For most consumers who have no relevant experience, purchasing through formal channels is the most secure, such as JD.com or Some certified stores.

At the same time, some brands of engine oil will have bar codes or anti-counterfeiting labels. By calling the phone number or sending a text message on the anti-counterfeiting label, we can also help us verify the authenticity of the oil. Of course, there are sometimes differences between real and fake engine oil in terms of packaging, appearance, smell, sealing, etc., but it may be difficult for non-professionals to grasp it, so the safest way is to buy it from a regular seller.

Question 2: How to observe the amount of engine oil in the car?

On the Internet, I often see some netizens debating whether it is more accurate to measure the oil in a hot car or in a cold car. , in fact, the correct way to observe the engine oil level is to measure the engine oil level on the ground when the car is cold. Before measuring, pull out the oil dipstick and wipe it clean, then reinsert the oil dipstick into the measuring hole. Make sure it is inserted all the way. Pull it out again to accurately check the oil level.

With the development of science and technology, more and more mechanical things are becoming electronic, and the oil dipstick is no exception. Nowadays, the electronic oil dipstick is no longer a new configuration. It can be used to observe the engine oil more calmly. With the surface height, there is no need to hold toilet paper to open the engine cover to observe. However, there is one detail that needs to be paid attention to when using this kind of electronic oil dipstick. That is, what is displayed on the display screen is not the entire scale, but the upper and lower limits. Therefore, if the bar indicator is almost "empty" on the display screen, It does not mean that there is no oil in the oil pan, but that the oil has reached the lower limit of the reasonable range and can be replenished in time.

Question 3: What are the methods for changing engine oil?

Some netizens asked that during maintenance at a 4S store, they saw workers draining the engine oil instead of draining it from the oil drain hole at the bottom of the car. Instead of using a pump to pump the oil out from above, I don't know if this method is correct. In fact, this way of pumping oil is not wrong. Pulling oil can clean out some dirt in the oil pan, and the effect is better than draining oil. Draining oil is easy to operate. Just put the car up and unscrew it. The oil drain screw on the oil pan will do the trick. Each of these two methods has its own benefits, it depends on which method is convenient for you.

Question 4: How to observe the life of engine oil?

We can use oil test paper to test whether the oil should be replaced. Just use the oil dipstick to dip a little oil from the oil tank and drop it on the test paper. Compare it with the instructions on the test strip package after 2 to 3 hours, and you will know clearly whether the oil needs to be changed.

Question 5: Are all cars suitable for adding fully synthetic engine oil?

What kind of engine oil should be added to a car is very particular. Many people think that fully synthetic engine oil is the best. Motor oil, so I use fully synthetic motor oil for my vehicle. In fact, adding fully synthetic engine oil is not the best choice. Full synthetic engine oil has better low-temperature fluidity, so its viscosity will be lower than semi-synthetic or mineral oil. For some vehicles that are older or have had their engines overhauled, For vehicles, because the piston in the engine is worn or the assembly is not precise after overhaul, the gap between the piston and the cylinder may be relatively large. If fully synthetic engine oil with a relatively low viscosity is used, the air tightness of the engine may be affected. It is easy to cause oil burning or gas blow-by.

Question 6: Can different brands of engine oil be mixed?

Each brand of engine oil has different additives. Mixing may cause deterioration of the chemical components. If conditions permit , we do not recommend mixing different brands of engine oil.

If it is some extreme situation, for example, you find that there is not much engine oil on the highway, but the engine oil sold in the service station is not the same brand as the one you use, in this case, you can mix it first, after all, the engine oil is It is much better than no oil, but choose the same type of oil and just change it as soon as possible afterwards.

Summary: The use of engine oil is very particular. The more expensive the engine oil, the better the effect. Therefore, when choosing engine oil, you must understand what kind of engine oil is suitable for your car.