As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING FLIGHT, ENROUTE, A STRONG ODOR OF OIL ENTERED THE CABIN. THE CREW DECIDED TO RETURN TO DEPARTURE WHERE AN UNEVENTFUL LANDING WAS MADE. INVESTIGATION IS ON-GOING, IT HAS NOT BEEN FULLY CONFIRMED IF THE OIL ODOR ORIGINATED FROM THE APU HOWEVER THE AIR INLET PLENUM WAS FOUND FRACTURED.