Oil change, filter and lube

An oil and filter change involves draining out the old motor oil and replacing it with fresh, new motor oil. The oil filter also gets replaced at the same time.

Oil undergoes thermal breakdown due to high operating temperature. When this occurs, the oil becomes less effective as a lubricant. And without a good lubricant parts of the engine rub together and wear each other out.

Oil also contains additives that have the ability to neutralize acids. Over time, these additives get used up and stop being effective.

Finally, oil can absorb water, dust and combustion byproducts and also hold them in suspension. Eventually, the oil gets saturated with these impurities and can't absorb any more. Then they remain in the engine and can cause corrosion.