Narrative:

30 mins after crew change (relief pilot and captain in seat); approximately 4 hours into flight; after shaking out cobwebs; I scanned the gauges and noticed oil quantity at 2 quarts. We checked the books and found no guidance in flight manual concerning no oil; so we checked engines section of flight manual. Minimal information about operating with no oil quantity. Book said ok as long as all other limits in normal range. Checked irregulars and found guidance on operating with high oil temperature; and also low oil pressure; both stating mandatory shutdown should temperature or pressure limits become exceeded. When oil quantity went to 1; about 20 mins later; we hacked clock and timed to zero. We discussed our options; all indicating we could continue as long as temperature and pressure were within limits; and called dispatch and maintenance. Maintenance advised the engine had at least 14 quarts when indicator read zero and as long as other indications were within limits; we could operate as normal. We discussed our diversion intentions with dispatch; should we need to if the engine deteriorated; and hatched several options should we need to. It was decided that should it become obvious the engine was deteriorating; we would think about making an early divert with 2 engines instead of waiting on it to quit. At XA15 the oil quantity went to zero and it was determined the engine was losing about 1.5-2.0 quarts an hour. Oil pressure and temperature were monitored throughout the remainder of flight and both were normal range for remainder. Normal approach and landing at approximately XF15. I went down to talk with the mechanics after landing. They said oil tank was empty; but could find no visible leaks upon initial inspection.

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Original NASA ASRS Text

Title: A B767-300 IN CRUISE AT FL330 NOTED LOW OIL QUANTITY IN 1 ENG. OIL PRESSURE AND TEMP WERE NORMAL AT FLT TERMINATION OIL TANK WAS EMPTY.

Narrative: 30 MINS AFTER CREW CHANGE (RELIEF PLT AND CAPT IN SEAT); APPROX 4 HRS INTO FLT; AFTER SHAKING OUT COBWEBS; I SCANNED THE GAUGES AND NOTICED OIL QUANTITY AT 2 QUARTS. WE CHKED THE BOOKS AND FOUND NO GUIDANCE IN FLT MANUAL CONCERNING NO OIL; SO WE CHKED ENGS SECTION OF FLT MANUAL. MINIMAL INFO ABOUT OPERATING WITH NO OIL QUANTITY. BOOK SAID OK AS LONG AS ALL OTHER LIMITS IN NORMAL RANGE. CHKED IRREGULARS AND FOUND GUIDANCE ON OPERATING WITH HIGH OIL TEMP; AND ALSO LOW OIL PRESSURE; BOTH STATING MANDATORY SHUTDOWN SHOULD TEMP OR PRESSURE LIMITS BECOME EXCEEDED. WHEN OIL QUANTITY WENT TO 1; ABOUT 20 MINS LATER; WE HACKED CLOCK AND TIMED TO ZERO. WE DISCUSSED OUR OPTIONS; ALL INDICATING WE COULD CONTINUE AS LONG AS TEMP AND PRESSURE WERE WITHIN LIMITS; AND CALLED DISPATCH AND MAINT. MAINT ADVISED THE ENG HAD AT LEAST 14 QUARTS WHEN INDICATOR READ ZERO AND AS LONG AS OTHER INDICATIONS WERE WITHIN LIMITS; WE COULD OPERATE AS NORMAL. WE DISCUSSED OUR DIVERSION INTENTIONS WITH DISPATCH; SHOULD WE NEED TO IF THE ENG DETERIORATED; AND HATCHED SEVERAL OPTIONS SHOULD WE NEED TO. IT WAS DECIDED THAT SHOULD IT BECOME OBVIOUS THE ENG WAS DETERIORATING; WE WOULD THINK ABOUT MAKING AN EARLY DIVERT WITH 2 ENGS INSTEAD OF WAITING ON IT TO QUIT. AT XA15 THE OIL QUANTITY WENT TO ZERO AND IT WAS DETERMINED THE ENG WAS LOSING ABOUT 1.5-2.0 QUARTS AN HR. OIL PRESSURE AND TEMP WERE MONITORED THROUGHOUT THE REMAINDER OF FLT AND BOTH WERE NORMAL RANGE FOR REMAINDER. NORMAL APCH AND LNDG AT APPROX XF15. I WENT DOWN TO TALK WITH THE MECHS AFTER LNDG. THEY SAID OIL TANK WAS EMPTY; BUT COULD FIND NO VISIBLE LEAKS UPON INITIAL INSPECTION.

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