As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL - FLT 12 - EN ROUTE PHL-MAD, AT APPROXIMATELY 50W LONGITUDE, THE CREW NOTED THAT THE LEFT ENGINE OIL PRESSURE WAS LOW AND THAT THE QTY WAS FLUCTUATING BETWEEN 13 AND 14. FLIGHT RETURNED TO PHL AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND A BAD O-RING ON THE LEFT ENGINE OIL CAP AND REPLACED IT. (M)