As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(AUS) OILY FUMES IN COCKPIT AND CABIN. AIRCRAFT TURNED BACK AND OVERWEIGHT LANDING WAS CARRIED OUT. OVERWEIGHT LANDING INSPECTION CARRIED OUT WITH NIL FAULTS. SUSPECT FUMES CAUSED BY INHIBITING FLUID REMAINING IN ENGINE FOLLOWING ENGINE CHANGE. INVESTIGATION CONTINUING. (CASA NR 510002061)