You should know the common sense of engine oil

Misunderstanding 1: when the oil turns black, it's time to change it
This understanding is not comprehensive. For the engine oil without dispersant, blackening is indeed a sign that the oil has seriously deteriorated, but the engine oil used in modern cars generally has dispersant added. The detergent washes the adhesive film and black carbon deposit on the piston and disperses them in the oil to reduce the generation of high-temperature deposits on the engine. Therefore, the color of engine oil tends to turn black after a period of use, but the oil is not completely deteriorated at this time.
Misunderstanding 2: add more oil if you can
The machine quantity should be controlled around the middle mark of the oil dipstick. Because too much oil will jump into the combustion chamber from the gap between the cylinder and piston to form carbon deposit. These deposits will increase the compression ratio of the engine and increase the tendency to produce knock; Carbon deposit is red hot in the cylinder, and it is easy to cause premature combustion. If it falls into the cylinder, it will aggravate the wear of cylinder and piston, and accelerate the pollution of engine oil. Secondly, too much oil increases the stirring resistance of the crankshaft and connecting rod, which increases the fuel consumption.
Mistake 3: oil often need not be changed
It is correct to check the engine oil frequently, but it can only make up for the shortage of engine oil quantity without replacing it, but it can not fully compensate for the loss of engine oil performance. Oil in the process of use, there will be a certain amount of consumption, so that the number of reduced, when the need for timely replenishment. At the same time, during the operation of engine oil, due to the harsh working environment, the oil will be polluted and oxidized, resulting in the gradual decline of oil performance. When the oil performance drops to a certain extent, it is not enough to provide the required lubrication protection for the engine. In order to better protect the engine, the engine oil should be replaced regularly.