There are ordinary, semi-synthetic and fully synthetic engine oils. As long as there is no "synthesis", it is "ordinary". The attenuation of engine oil is limited by time, and it generally begins to oxidize after being exposed to air for 3 months. In other words, the oil should be changed once every 3 months, and the synthesis time is 6-9 months. If you drive a car, it generally begins to decay after 5000 kilometers in China. Semi-synthesis is generally 7500 km, and total synthesis is generally about 10000 km. Therefore, it is generally believed that the first thing to change oil is the mileage (provided that there is no traffic jam):

Ordinary 5000 kilometers

Semi-synthetic 7500 km

The total becomes 10000 km.

Second, how to change?

The maintenance man outside directly unscrewed the screw to drain the oil, removed the machine filter and replaced it with new oil, and then forget it. Actually, it is not. When the oil was drained for the first time, even if it didn't flow out, there was still old oil in the engine block and oil pump. If new oil is added immediately, it will soon turn black because of mixing with old oil, which will affect the performance of oil. The correct step should be to drain the old engine oil, pour in 4L engine oil, turn off the engine after idling for 25 minutes, and then pour out the high-quality engine oil to be used this time. This is a cleaning step. To clean the oil, just pour in cheap new engine oil (imitation engine oil is also acceptable). It is ok to use inferior engine oil, but it must be new, because just to idle for 20 minutes to take out the old engine oil that can't be released is equivalent to drinking coke, and there is still some coke in the bottle that can't be poured out. At this time, you add some water, shake the bottle and pour it out, and the bottle will be clean. In the same way. After idling for 20 minutes, let off the inferior engine oil for cleaning (you can find that the engine oil for cleaning will turn black after 20 minutes, just because the residual engine oil is brought out). By the way, change the filter and blow it with an air gun if possible. Then check the oil drain screw and machine filter, and pour in the high-quality engine oil for this maintenance after confirming that it has been tightened. Check the oil level while adding it, and then check whether there is oil leakage after adding it. This is the most standard step.

Third, if the price is right, the medium-sized regular auto repair factory in the second-tier provincial capital cities will have its own oil filter working time fee of 50 yuan, and the oil filter in the auto repair factory will be free of working time fee. In fact, the oil price in his house is not high, but it is not very reassuring. Only change oil and filter 20, change oil+filter 50, and take it back and forth.