Inside a refrigerator, there is bound to be some condensation, and not every part of the oil is going always moving, so I imagine if he keeps it running long enough, margarine will start to form in all the little crevices.
I think this is a very cool idea, and a great project. For everyday use, though, not so sure. I just think that this is bound to eventually cause some kind of problems. And even if it didn't, a fridge dosen't fit under my desk as well as the computer case.
18* C... that's incredible. Mine idles at like 35.
and oil is a lubricant, so it woulden't wear down anything thats moving.
upgrading would be a huge pain with that.
but, coulden't you have pretty much the same resaults by just having the pc in the frige without the oil? it'd basicly be a temperature controlled environment like net centers use for the racked PCs.