I think the oils all serve different purposes.
Fish oil is a source of Omega 3's. Denna gets a human sized dose daily (2 capsules of
this stuff)
Coconut oil is a source of Lauric acid, which can help boost the immune system - Denna finds is very, very tasty, but doesn't get it on a regular basis
From dheepakh's mix - which looks very intriguing!
Flax is also a source of Omega 3's
Wheatgerm oil is a good source of Vitamin E
Olive Oil contains oleic acid which may have some health benefits - we don't feed this one, so had to google it - found this article:
8 Reasons to Add Olive Oil to Your Dogs Diet | Dogster
I might have to start mixing things up for Denna a bit more - thanks for sharing your recipe , Dheepakh!