How to sell automobile lubricating oil well?

I suggest you know more about the car, which parts of the car need what lubricating oil, the working principles of gasoline engines and diesel engines, the lubrication mechanism of lubricating oil, the basic concepts of SAE API API, and the advantages and disadvantages of other brands of lubricating oil. I believe that after you have mastered this knowledge, you will be able to sell lubricants with ease.