Why do car dealers just take their cars back for oil change?

The reasons why the car dealer needs to change the oil as soon as he gets it back are as follows:

The core components of automobile are engine and gearbox, and engine oil plays an indispensable role in helping these metal-based components work smoothly. Because it can play the role of lubrication, heat dissipation and cleaning, if you buy a used car, the first thing to do is to change the oil for the car. In addition, the "blood" to be replaced also includes gearbox oil, brake oil, water tank cooling water, water splashed with sodium silicate and so on. Transmission oil is the most easily overlooked item. It is recommended that the owner change the gearbox oil that meets the specifications of the vehicle manufacturer immediately after driving the used car, whether it is manual or automatic. It is especially important for used cars with a car age of 5 years or more.