Narrative:

On preflight inspection the oil level was found to be slightly less than the 6 quart recommended operating min, and 2 quarts of oil were added. The oil filler cap was replaced. The flight was begun without incident and all system appeared to function normally. Approximately 1 hour and 30 mins into the flight, a small amount of oil suddenly appeared on the windshield. At this time the oil pressure and oil temperature were both well into the normal range. My exact position was unknown, as there were no prominent landmarks nearby. I was able to tell that I was along the white river, but I was uncertain how far down the river I had progressed. I attempted to contact little rock (adams field) approach, but my altitude was relatively low and I was still some distance from the arsa. I decided not to risk further delay in obtaining assistance. I called on 121.5 as I began to climb to increase radio range. Little rock approach responded through another radio outlet. I was instructed to squawk XX00 to aid in radar location of my aircraft and vectors to the nearest airport, which was in searcy, ar, were given. As we proceeded to the airport, the oil pressure began to decrease, and had reached the bottom of the 'green arc' as we turned on final for searcy. Oil temperature did not increase measurably. Landing was accomplished without incident on the first attempt. Inspection of the engine after landing demonstrated that the oil filler cap had come fully off in flight. The filler cap was secured to the spout by a chain, and was thus still in the engine compartment. A substantial amount of oil was present on the port side of the aircraft.

Related reports:

Google
 

Original NASA ASRS Text

Title: LOSS OIL DIVERT TO NEAREST ARPT.

Narrative: ON PREFLT INSPECTION THE OIL LEVEL WAS FOUND TO BE SLIGHTLY LESS THAN THE 6 QUART RECOMMENDED OPERATING MIN, AND 2 QUARTS OF OIL WERE ADDED. THE OIL FILLER CAP WAS REPLACED. THE FLT WAS BEGUN WITHOUT INCIDENT AND ALL SYS APPEARED TO FUNCTION NORMALLY. APPROX 1 HR AND 30 MINS INTO THE FLT, A SMALL AMOUNT OF OIL SUDDENLY APPEARED ON THE WINDSHIELD. AT THIS TIME THE OIL PRESSURE AND OIL TEMP WERE BOTH WELL INTO THE NORMAL RANGE. MY EXACT POS WAS UNKNOWN, AS THERE WERE NO PROMINENT LANDMARKS NEARBY. I WAS ABLE TO TELL THAT I WAS ALONG THE WHITE RIVER, BUT I WAS UNCERTAIN HOW FAR DOWN THE RIVER I HAD PROGRESSED. I ATTEMPTED TO CONTACT LITTLE ROCK (ADAMS FIELD) APCH, BUT MY ALT WAS RELATIVELY LOW AND I WAS STILL SOME DISTANCE FROM THE ARSA. I DECIDED NOT TO RISK FURTHER DELAY IN OBTAINING ASSISTANCE. I CALLED ON 121.5 AS I BEGAN TO CLB TO INCREASE RADIO RANGE. LITTLE ROCK APCH RESPONDED THROUGH ANOTHER RADIO OUTLET. I WAS INSTRUCTED TO Squawk XX00 TO AID IN RADAR LOCATION OF MY ACFT AND VECTORS TO THE NEAREST ARPT, WHICH WAS IN SEARCY, AR, WERE GIVEN. AS WE PROCEEDED TO THE ARPT, THE OIL PRESSURE BEGAN TO DECREASE, AND HAD REACHED THE BOTTOM OF THE 'GREEN ARC' AS WE TURNED ON FINAL FOR SEARCY. OIL TEMP DID NOT INCREASE MEASURABLY. LNDG WAS ACCOMPLISHED WITHOUT INCIDENT ON THE FIRST ATTEMPT. INSPECTION OF THE ENG AFTER LNDG DEMONSTRATED THAT THE OIL FILLER CAP HAD COME FULLY OFF IN FLT. THE FILLER CAP WAS SECURED TO THE SPOUT BY A CHAIN, AND WAS THUS STILL IN THE ENG COMPARTMENT. A SUBSTANTIAL AMOUNT OF OIL WAS PRESENT ON THE PORT SIDE OF THE ACFT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.