I always throw away the oil cap: A colleague explained to me what it is actually for

Now I’ll tell you everything in detail. The fact is, the plug needs to be put back in place, but first, you have to put it back.

Then press the cork into the bottle so that it is fixed between the slots.

Since the plug is asymmetrical, there is always a small gap.

In this space the oil can be measured, i.e. it is poured out in a thin stream.

Then press the cap into the bottle so that it’s secured between the slots. Because the plug is asymmetrical, a small gap always remains.

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