I had this problem with my pads... i think the oil might come from road grime and residue oil on the road, to fix the situation i tried using rubbing alchohol, but it didn't work to great. i then went to my LBS and they did the same and tried to clean the pads, but that still didn't work. then i thought "fuck it" and went to the local hardware store and he recomended some 'Caustic soda'....and it worked a treat. just buy some, mix it up and use an old toothbrush to rub it on (wear gloves though, its really corosive). the best thing is its cheap and as far as i know, hasn't ruined the pads, this is almost 2 months later.