So as I understand it your running a cooled water loop to a pc submerged in mineral oil.
One problem I can see with this is that the mineral oil temp will go up because of other components like the chipset and ram.....so this will affect your cooling loop temps by conduction through the tubes and exterior of your water blocks so you may need to thermally insulate those.
You make also need to have some means to cool the mineral oil separately from the water loop.
Here is a great link for a guy that has done a really icy water loop.
He has used a window air con unit to make a super chilled external reservoir which he pumped to his pc sealed in a chill box.
He did have a lot of problems with pump failures though....probably due to condensation as they were externally house and he ended up submerging those in vegie oil.
But although long that post is well worth reading through for you....contains all the best info on fluid mix etc.
Tbh though I think the best method for this would be to forget the mineral oil......you would have to use special tubing which is expensive and as stated you would have to insuate your cooling loop from the oil and have a separate cooling loop for the oil.#
By far the simplest method would be to go for a chill box made from an window type ac unit and include an internal water loop.
It's comparatively very simple and would be very effective.
If your interested I'll go into more detail for you.