What was found
APPROX 2 MIN AFTER TAKEOFF FROM PAKN I NOTICED SMOKE IN THE COCKPIT AND BEGAN TO HEAD BACK THE AIRPORT. APPROX 30 SEC AFTER THE FIRST INDICATION OF SMOKE I HAD APPROXIMATELY A 50% REDUCTION IN POWER AND THE ENGINE BEGAN RUNNING ROUGH. BEFORE LANDING I WAS AT FULL POWER AND DESCENDING SLOWLY. I WAS ABLE TO LAND SAFELY ON 18 AND TAXI BACK TO THE RAMP. WHEN I GOT BACK TO THE RAMP AND EXITED THE AIRCRAFT, THERE WAS A LARGE OIL STREAM ON THE RIGHT SIDE OF THE FUSELAGE AND THERE WAS A SMALL TRAIL OF OIL FOLLOWING THE AIRCRAFT. WE HAD SMOKE IN THE COCKPIT FROM THE OIL LOSS IN THE ENGINE.