Will the engine oil be damaged if the oil is not cleaned when changing the oil?

When we usually do maintenance and change the oil, the auto repair shop usually lifts the car with a lift to drain the old oil and change the new oil. However, many car owners find that some oil will be left after each maintenance. What is going on? Did the auto repair shop drain the engine oil? How to use the remaining new engine oil? How can we make this extra engine oil play its value?

Why is there always "some left" when changing engine oil?

1. Gravity reason, normal phenomenon If the car is raised by a lift, the old oil flows out naturally by gravity. Due to the angle of the oil outlet and the irregular structure of the oil pan, there is always a part of the oil that cannot flow out naturally. Because the engine oil is used for a long time, there are many impurities, and it cannot be completely cleaned. If you open the oil pan, you can see that, for example, there is still some oil on the crankshaft and connecting rod. This oil cannot be drained clean by gravity . Of course, many auto repair shops now also use pumping units to extract old oil, which may be cleaner. In short, it is normal for a little oil to remain. In addition, there are many ways to lubricate the engine. Some parts cannot be lubricated normally due to the mechanical structure. They can only rely on the constant circular movement of the crankshaft balance weight and the bottom of the connecting rod to splash the oil to the lubrication area, such as the valve, the top pillar, and the cylinder wall. Wait, if everything is cleaned, it will damage the engine when starting . Of course, there are also some black-hearted roadside shops that don’t drain the engine oil cleanly and resell the remaining engine oil, but this is a minority after all. Generally, auto repair shops are helping car owners to change the oil. Even if the new oil is not filled up, they will be brought back by the car owner. Will the engine oil be damaged if it is not drained cleanly ? Although it is normal for a little oil to remain, the owner and friends cannot help but wonder whether the remaining old oil will damage the engine? In fact, everyone is simply too worried. The oil has the functions of cleaning, lubricating, cooling, anti-corrosion, sealing, etc. The metal debris generated by the internal wear of the engine can be retained in the oil pan along with the oil circulation, because the oil pan is the oil pump When the oil is delivered to the upper part of the engine, the oil will be filtered, and then the oil will enter the lubricating oil passage, so there will be no damage to the inside of the engine . In addition, during engine operation, the engine oil is affected by the fuel combustion temperature and the catalytic action of various media and metals. It will gradually deteriorate and age, resulting in carbon deposits, paint film and sludge that will be harmful to the engine. Therefore, it must be regularly Clean up the lubrication system and clean up the residual oil to ensure the "health" of the engine! How to use the remaining new engine oil? First of all, let's briefly understand why the engine oil deteriorates : Under normal circumstances, the oil-containing water, an amount of 0.03% or less, when the water content exceeds 0.1%, the oil additive will fail to accelerate the oxidation process of the oil, and thus increase the engine may generate corrosive inorganic acids; Secondly, " oxygen " is also the main factor affecting various additives in engine oil, especially in the case of sunlight or high temperature, the oxygen in the air reacts faster with engine oil; The impurities mainly affect the cleanliness of the engine oil. The impurities mixed in the engine oil will affect the lubricating effect of the engine oil, and even cause abnormal wear of the engine, which in turn affects its sealing performance and even burns the engine oil. Ps: If the car owner fills the deteriorating engine oil into the vehicle, the parts that need to be lubricated and cooled in the engine will not be adequately protected, and the load and wear of the engine will increase, eventually resulting in increased engine wear, and overhaul is not impossible. . In fact, ordinary engine oil generally has a shelf life of 4 to 5 years in the unopened state. Therefore, the unopened engine oil can be stored for a longer time and can be used again by tightening the lid . preservation method Cover the mouth of the oil bottle with a layer of plastic film, and then screw on the oil bottle cap. Pay attention to maintaining the tightness of the bottle mouth, choose a thicker plastic film, and then drop wax to seal, otherwise it will be difficult to isolate the air. Put the sealed oil in a cool and dry place, so as to avoid the deterioration of the oil due to oxidation reaction, such as wall corners. Of course, there are still many car owners who like to put it in the trunk, which is also possible in case of emergency. Engine oil that has been sealed for a long time will inevitably have moisture and impurities, so it must not be shaken before use. When adding the engine oil, do not pour it all in. There will be a small amount of water or impurities at the bottom of the bottle. Adding it to the engine will affect its performance or even produce adverse effects. So add engine oil to keep a small part of the bottom of the bottle, so that all moisture and impurities remain in the bottle! Although the method is right, the oil can be stored for a long time, but Xiaobang recommends that it is best to use it as soon as possible within six months . For example, when checking the oil dipstick, it is found that the oil is lacking, which happens to come in handy. In addition, every time you do maintenance, let the master use the remaining oil from the last time, and then use the new oil, so that the remaining oil is up to date, so there is no need to worry about deterioration.