Narrative:

Enroute at FL380; oil quantity on the left engine decreased from approximately 12 to 0 in less than 5 minutes. All other engine indications were normal. We sent a message to maintenance describing the indications. After a short time; oil pressure also began to decrease. While the captain contacted maintenance and dispatch; the oil pressure dropped even more to less than 60 psi with a low oil pressure light and left engine low oil pressure EICAS message. The captain conferred with dispatch and maintenance and settled on diverting. While the captain and 777 first officer jump-seater ran the checklists for both the engine oil pressure EICAS message and in-flight engine shutdown; I declared an emergency with ATC and initiated a descent and vectors toward the divert airport. I requested to have emergency equipment standing by on arrival. The left engine was shutdown during descent per the flight manual.

Google
 

Original NASA ASRS Text

Title: A B757 lost engine oil in cruise and a short time later the oil pressure decreased. The engine was shut down; an emergency declared and the flight diverted to a nearby airport.

Narrative: Enroute at FL380; oil quantity on the left engine decreased from approximately 12 to 0 in less than 5 minutes. All other engine indications were normal. We sent a message to maintenance describing the indications. After a short time; oil pressure also began to decrease. While the Captain contacted Maintenance and Dispatch; the oil pressure dropped even more to less than 60 PSI with a low oil pressure light and left engine low oil pressure EICAS message. The Captain conferred with Dispatch and maintenance and settled on diverting. While the Captain and 777 First Officer jump-seater ran the checklists for both the engine oil pressure EICAS message and in-flight engine shutdown; I declared an emergency with ATC and initiated a descent and vectors toward the divert airport. I requested to have emergency equipment standing by on arrival. The left engine was shutdown during descent per the flight manual.

Data retrieved from NASA's ASRS site as of April 2012 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.