The present invention includes methods and systems for improving oil quality of a contaminated oil mixture by removing contaminants from a contaminated oil comprising the steps of: pretreating a membrane contactor system having a first and a second surface with an hydrophobic liquid, wherein the hydrophobic liquid is contacted to at least one of the first and second surfaces; obtaining a contaminated oil that comprises oil and lipophobic contaminants; contacting the contaminated oil onto a first surface of one or more membrane contactors to coalesce the oil on the first surface; and collecting the coalesced oil from the contaminated oil on the second surface of the membrane contactor.