Narrative:

At 3500' on 017 degree radial 6 SM from sjc VOR, I noticed a trickle of oil on cowling. These engines are leakers, but this was unusual. I decided to land and investigate immediately, as loss of oil and engine failure seemed like a possibility. Thought sjc airport was as close as the closed fremont airport (Q59), the area around it is densely populated. Being familiar with fremont airport I felt safer with the many open fields between the airport and myself since engine failure seemed possible. Flight was direct from approximately 6 mi on sjc's 017 degree radial to fremont airport. This may have brought me through a corner of the sjc arsa. Being in the final approach phase I was too busy doing checklists and evaluating en route landing options to call ATC (a possible airspace violation). Upon landing I located a mechanic who identified the problem. An oil filter line (military 6000 hose) covered by silicone/fiberglass firesleeve had deteriorated in a location near the exhaust manifold and started seeping oil. Oil loss was actually minimal. In the roughly 3 min it took to land the plane I had more than enough to do with checklists and planning my precautionary landing. Communicating was not necessary for safety, and would have probably reduced it. In preflting, the firesleeve showed little sign of the problem hiding underneath (slight discoloration at most). My preflts will be much more meticulous.

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Original NASA ASRS Text

Title: GA SMA PRECAUTIONARY LNDG DUE TRICKLE OF OIL ON ENGINE COWL. UNAUTH PENETRATION OF SJC ARSA.

Narrative: AT 3500' ON 017 DEG RADIAL 6 SM FROM SJC VOR, I NOTICED A TRICKLE OF OIL ON COWLING. THESE ENGINES ARE LEAKERS, BUT THIS WAS UNUSUAL. I DECIDED TO LAND AND INVESTIGATE IMMEDIATELY, AS LOSS OF OIL AND ENGINE FAILURE SEEMED LIKE A POSSIBILITY. THOUGHT SJC ARPT WAS AS CLOSE AS THE CLOSED FREMONT ARPT (Q59), THE AREA AROUND IT IS DENSELY POPULATED. BEING FAMILIAR WITH FREMONT ARPT I FELT SAFER WITH THE MANY OPEN FIELDS BETWEEN THE ARPT AND MYSELF SINCE ENGINE FAILURE SEEMED POSSIBLE. FLT WAS DIRECT FROM APPROX 6 MI ON SJC'S 017 DEG RADIAL TO FREMONT ARPT. THIS MAY HAVE BROUGHT ME THROUGH A CORNER OF THE SJC ARSA. BEING IN THE FINAL APCH PHASE I WAS TOO BUSY DOING CHECKLISTS AND EVALUATING ENRTE LNDG OPTIONS TO CALL ATC (A POSSIBLE AIRSPACE VIOLATION). UPON LNDG I LOCATED A MECHANIC WHO IDENTIFIED THE PROBLEM. AN OIL FILTER LINE (MIL 6000 HOSE) COVERED BY SILICONE/FIBERGLASS FIRESLEEVE HAD DETERIORATED IN A LOCATION NEAR THE EXHAUST MANIFOLD AND STARTED SEEPING OIL. OIL LOSS WAS ACTUALLY MINIMAL. IN THE ROUGHLY 3 MIN IT TOOK TO LAND THE PLANE I HAD MORE THAN ENOUGH TO DO WITH CHECKLISTS AND PLANNING MY PRECAUTIONARY LNDG. COMMUNICATING WAS NOT NECESSARY FOR SAFETY, AND WOULD HAVE PROBABLY REDUCED IT. IN PREFLTING, THE FIRESLEEVE SHOWED LITTLE SIGN OF THE PROBLEM HIDING UNDERNEATH (SLIGHT DISCOLORATION AT MOST). MY PREFLTS WILL BE MUCH MORE METICULOUS.

Data retrieved from NASA's ASRS site as of August 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.