Before this became the de factor standard in tech dive computers, advanced divers would often do the same and fill their units with mineral oil.
For anyone interested in how this can go wrong, Raising the Dead - a book about scuba diving at its limits - has a passage about a rescue diver repairing his dive computer in the field, re-filling the oil, and noticing that he'd lost a drop or two in the process, with a resulting tiny air bubble...
For anyone interested in how this can go wrong, Raising the Dead - a book about scuba diving at its limits - has a passage about a rescue diver repairing his dive computer in the field, re-filling the oil, and noticing that he'd lost a drop or two in the process, with a resulting tiny air bubble...