As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE PILOT CONDUCTED A NORMAL PREFLIGHT. APPROXIMATELY 35 MINUTES AFTER TAKE OFF, THE PILOT NOTICED AN OIL PRESSURE DROP, AND DECLARED AN EMERGENCY. THE PILOT LANDED SAFELY. THE AIRCRAFT'S BELLY WAS FOUND COVERED IN OIL. FURTHER INSPECTION SHOWED THE OIL LEAK COMING FROM THE REAR RIGHT OIL COOLER COOLING FINS.