Abstract: The filter assembly removes minute soot particles from diesel engine oil during service. It may be used to remove other minute particles from various oils. A charged metal screen, with a mesh size preferably in the range of 2 to 4 holes per linear inch, causes attraction of the minute soot particles. The electric potential causes the particles coagulate to form larger masses which may be filtered by an electrically non-conductive filtering element. Particles also collect on the mesh surface. A D.C electric potential is applied to the screen to create an average electric potential of about 250 or more V/mm between the screen and the grounded electrode.