Narrative:

After leveling off at FL350; noticed #1 engine oil quantity 1.7 gals. Limit of 1.5 en route and log history prompted a discussion and flight manual review. After testing gauge; directed flight attendant to check exterior of #1 engine. Flight attendant reported oil coming out like a spigot. Sent a call me message to dispatch but was successful in contacting both dispatch and maintenance. Request WX and NOTAMS for ZZZ and had dispatch alert ZZZ operations of our expected arrival. Informed maintenance that preflight log history indicated that #1 engine had a starter pad seal changed that morning due to oil leak after shutdown. By then; oil was 1.4 and failing; so I had first officer changed destination in route page while I issued a cabin advisory and informed passenger. Requested priority handling and equipment from ATC which gave us vectors and a descent to FL240. Descended at flight idle while monitoring oil quantity. Briefed first officer on single engine approach contingency. Planned target N1 78% and flaps 2 degrees to FAF in the event oil temperature went above 165 degrees or oil pressure below 13 psi. Made a final PA to passenger approximately 14000 ft and touched base with flight attendant again at 12000 ft to reassure normal landing and address any last min issues. Deployed gear at 8000 ft. Briefed first officer on keeping #1 engine at flight idle to around 500 ft AGL. Flew approach approximately 10 KTS above target and used minimum thrust on #1 engine from 300 ft. Captain landed uneventfully and secured #1 engine upon exiting runway. Both oil pressure and oil temperature were normal upon shutdown. Oil quantity was slightly above 1 gal. Pwred #1 generator bus with APU and taxied to deice pad. Had fire marshall assess engine and determined leak would not present undue contamination to taxi and ramp surfaces. Proceeded to gate and briefed passenger. After deboarding passenger; briefed contract maintenance tech on recent maintenance activity. He added 3 gals of oil to #1 engine and opened external start valve to determine location of oil leak. When unable to determine location; maintenance tech solicited crew to participate in high power engine run. I declined due to possible fire or engine damage; and felt this task would be better served by maintenance. We did however; participate in towing the aircraft off of the gate to remote parking. At that point; I contacted maintenance engine controller to provide details and confirm proper write-ups were established. We anticipate that the starter pad seal may not have been properly seated and expect no damage to engine. After discussing the events with flight manager we found an alternate crew willing to complete the trip and elected to remove ourselves from subsequent flts. We were both wired to complete the mission; but had to consider real distrs; a 3:30 am wake up call; and a long duty day ahead. I was also flying day 11 out of 12 with 1 day off. We chose the safe conservative decision. FM provided full support of the flight office which was greatly appreciated and in concert with their strong reputation.

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Original NASA ASRS Text

Title: B737 FLT CREW AT FL350 DETECTS DECREASING OIL QUANTITY AND ELECTS TO DIVERT TO NEAREST SUITABLE ARPT FOR UNEVENTFUL LANDING.

Narrative: AFTER LEVELING OFF AT FL350; NOTICED #1 ENG OIL QUANTITY 1.7 GALS. LIMIT OF 1.5 ENRTE AND LOG HISTORY PROMPTED A DISCUSSION AND FLT MANUAL REVIEW. AFTER TESTING GAUGE; DIRECTED FLT ATTENDANT TO CHK EXTERIOR OF #1 ENG. FLT ATTENDANT RPTED OIL COMING OUT LIKE A SPIGOT. SENT A CALL ME MESSAGE TO DISPATCH BUT WAS SUCCESSFUL IN CONTACTING BOTH DISPATCH AND MAINT. REQUEST WX AND NOTAMS FOR ZZZ AND HAD DISPATCH ALERT ZZZ OPS OF OUR EXPECTED ARR. INFORMED MAINT THAT PREFLT LOG HISTORY INDICATED THAT #1 ENG HAD A STARTER PAD SEAL CHANGED THAT MORNING DUE TO OIL LEAK AFTER SHUTDOWN. BY THEN; OIL WAS 1.4 AND FAILING; SO I HAD FO CHANGED DEST IN RTE PAGE WHILE I ISSUED A CABIN ADVISORY AND INFORMED PAX. REQUESTED PRIORITY HANDLING AND EQUIP FROM ATC WHICH GAVE US VECTORS AND A DSCNT TO FL240. DSNDED AT FLT IDLE WHILE MONITORING OIL QUANTITY. BRIEFED FO ON SINGLE ENG APCH CONTINGENCY. PLANNED TARGET N1 78% AND FLAPS 2 DEGS TO FAF IN THE EVENT OIL TEMP WENT ABOVE 165 DEGS OR OIL PRESSURE BELOW 13 PSI. MADE A FINAL PA TO PAX APPROX 14000 FT AND TOUCHED BASE WITH FLT ATTENDANT AGAIN AT 12000 FT TO REASSURE NORMAL LNDG AND ADDRESS ANY LAST MIN ISSUES. DEPLOYED GEAR AT 8000 FT. BRIEFED FO ON KEEPING #1 ENG AT FLT IDLE TO AROUND 500 FT AGL. FLEW APCH APPROX 10 KTS ABOVE TARGET AND USED MINIMUM THRUST ON #1 ENG FROM 300 FT. CAPT LANDED UNEVENTFULLY AND SECURED #1 ENG UPON EXITING RWY. BOTH OIL PRESSURE AND OIL TEMP WERE NORMAL UPON SHUTDOWN. OIL QUANTITY WAS SLIGHTLY ABOVE 1 GAL. PWRED #1 GENERATOR BUS WITH APU AND TAXIED TO DEICE PAD. HAD FIRE MARSHALL ASSESS ENG AND DETERMINED LEAK WOULD NOT PRESENT UNDUE CONTAMINATION TO TAXI AND RAMP SURFACES. PROCEEDED TO GATE AND BRIEFED PAX. AFTER DEBOARDING PAX; BRIEFED CONTRACT MAINT TECH ON RECENT MAINT ACTIVITY. HE ADDED 3 GALS OF OIL TO #1 ENG AND OPENED EXTERNAL START VALVE TO DETERMINE LOCATION OF OIL LEAK. WHEN UNABLE TO DETERMINE LOCATION; MAINT TECH SOLICITED CREW TO PARTICIPATE IN HIGH PWR ENG RUN. I DECLINED DUE TO POSSIBLE FIRE OR ENG DAMAGE; AND FELT THIS TASK WOULD BE BETTER SERVED BY MAINT. WE DID HOWEVER; PARTICIPATE IN TOWING THE ACFT OFF OF THE GATE TO REMOTE PARKING. AT THAT POINT; I CONTACTED MAINT ENG CTLR TO PROVIDE DETAILS AND CONFIRM PROPER WRITE-UPS WERE ESTABLISHED. WE ANTICIPATE THAT THE STARTER PAD SEAL MAY NOT HAVE BEEN PROPERLY SEATED AND EXPECT NO DAMAGE TO ENG. AFTER DISCUSSING THE EVENTS WITH FLT MGR WE FOUND AN ALTERNATE CREW WILLING TO COMPLETE THE TRIP AND ELECTED TO REMOVE OURSELVES FROM SUBSEQUENT FLTS. WE WERE BOTH WIRED TO COMPLETE THE MISSION; BUT HAD TO CONSIDER REAL DISTRS; A 3:30 AM WAKE UP CALL; AND A LONG DUTY DAY AHEAD. I WAS ALSO FLYING DAY 11 OUT OF 12 WITH 1 DAY OFF. WE CHOSE THE SAFE CONSERVATIVE DECISION. FM PROVIDED FULL SUPPORT OF THE FLT OFFICE WHICH WAS GREATLY APPRECIATED AND IN CONCERT WITH THEIR STRONG REPUTATION.

Data retrieved from NASA's ASRS site as of May 2009 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.