The probable causes for this condition are worn pump bearings, or a worn engine shaft seal. CAUTION: Do not continue to operate the pressure washer if it is leaking oil until the cause has been determined and corrected. Irreparable damage can occur to the unit if it continues to run in this condition. This is an occurrence that requires disassembly of the pump and manifold. If your unit is under warranty, take it into the nearest Campbell Hausfeld service center. If it is not under warranty, you should take it into the nearest service center or call Campbell Hausfeld Technical Support at (800) 543-6400.