As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE B NUT ON THE OIL RETURN LINE FROM THE #1 CYLINDER WAS FOUND TO BE LOOSE. OIL WAS LEAKING FORM THIS LOCATION AND SOME WAS NOTED ON THE LEADING EDGE OF THE RH WING FROM THE AIR FLOW. REMOVED THE UPPER COWLING AND TIGHTEN BUT B NUT. RAN THE ENGINE ON THE GROUND TO TEST FOR LEAKS. NONE NOTED. RE INSTALLED THE UPPER COWL AND RETURNED THE AIRCRAFT TO SERVICE.