I had this problem in my D3... Oil on the mirror... Went once to clean under warranty, but I was hoping for an explanation of some sort and actually some action to prevent future oil splashes. No explanation at all and no action. 500 shots later the oil came back. After a few iterations, I stopped using the D3 that otherwise I loved to pieces... It was like take your car to an oil change every week. Not convenient. Nikon (which I love) disappointed me bitterly.
Eye Fi is terrible. Spent the money to install it on my Oly XZ1, and it never worked. Complete waste of time and money (almost 100 Euro). How can they claim patents for a technology that doesn't work?
Check this link: http://support.eye.fi/cameras/olympus/xz-1
So, according to Eye-fi, It should work OK. Instead, it is painfully slow, I mean slow measured in hours, not minutes, and it makes the camera freeze, and the battery overheat to extreme temperatures.