Mineral oil cooling is not all that practical or efficient. Been tried eons ago. Many more cons than advantages. Its more of  "oh hey, look what I did". Initial temps are great.....until the oil starts to heat up.
CONS
1) The weight alone of the system.
2) The enclosure would have to be air-tight and purged with nitrogen or similar. Impurities and moisture from air over time can cause the oil to become electrically conductive..........not good.
3) The oil would still have to be cooled somehow, such as thru a radiator or some sort of heat-exchanger. If not, temperature will reach an equilibrium and begin to overheat. Defeating the purpose.
4) After you realize it was a complete f%&k-up, your components are now covered in oil and very difficult to clean.
 
ADVANTAGES
Ummm, it might look cool if done properly. Other than that....none.
 
Just my take. There are good reasons nobody does it.

An alternative that some people use is 3m low temp boiling non-conductive liquid - which boils at a low temp like 40c, and then can condense in a chamber above the components.  It has to be sealed, and there are many more issues to cover - but it is possible, and some people do actually do this sort of thing - but it is far from practical or routine.