Until recently always ran k and n panel.filters and never oiled them, I know you can clean and re oil them and get a oil kit to do it but just bought new ones as don't fancy applying oil manually myself or washing them, for money they cost I just always bought a new one, just my opinion and never had any trouble with MAFs etc.I've had various types of panel filters down through the years I wash them out but never oil them any views on this.