I always threw away the oil plug: a colleague told me what it was really needed for

Now I will tell you everything in detail. The fact is that the plug needs to be returned to its place, but before that you need to turn it upside down.

After this, press the cap inside the bottle so that it is fixed between the slots. Since the plug is asymmetrical, there is always a small gap left.

This gap helps to dose the oil, that is, it will be poured in a thin stream.