You still need to cool the oil.

The thing is the oil has a HUGE thermal capacity, and it'll take up to 8-12 hours to heat up, but it can and will eventually hit critical temperatures if not properly cooled. A poor choice (IMO) for 24/7 dedicated mining. There are silent/efficient ways to cool the oil, but don't think that just using mineral oil is a magical solution

Oil cooling can be a real sweet deal for home computers, though, as the computer will be turned off before the oil heats up.