I was just reading yesterday about another case too - https://forums.watchuseek.com/f2/my-oiled-casio-f-91-dives-d...

He seems to mention purposefully creating an air bubble in the enclosure (by letting a few drops of the oil drip out) — why would he want to do that??

> "I slightly loosen two screws, to let out a couple of drops of oil (which would allow forming a bubble inside the box)."

If the oil expands and contracts with temperature then the bubble would allow this without the oil blowing the seal.

I think that’s the idea. Could be wrong.