Large Transport
Maintenance Airframe; Maintenance Powerplant
Communication Breakdown; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Company Policy; Procedure; Human Factors
After block in I started my ETOPS check and immediately noticed a puddle of oil under the Left engine. The Rolls Royce RB211 is a very stingy engine for oil consumption and external leaks are almost never visible. The cowling is clean and they rarely drip on the ground. I went to the cockpit and found 16 quarts indicated on the EICAS engine display; the right engine showed 21 quarts (normal quantity). The co-pilot was outside the cockpit; so I stepped out to ask him if he had noticed the left engine oil quantity. He was vague in his recollection but did remember seeing the 16 quart indication. Neither crew member had written it up which I thought rather strange since it was below ETOPS limits for the return flight. I researched the logbook for oil consumption and found a consistently high amount of oil being added for at least the prior 5 days. We serviced the left engine with 4 more quarts in Airport ZZZ after a 5 hour flight from Airport ZZZ1 again. The engine was consistently leaking large quantities of oil but no one caught it or stopped the plane from flying ETOPS. It was leaking from the IDG drive shaft drain because the O-ring on the drive shaft was cut and almost 1-4 of the circumference was missing half its diameter I do not understand how so many pilots or mechanics did not recognize the high consumption rate or see the leak under the engine. The Oil Monitoring Program did not flag the consumption because it is triggering point of 8 quarts added at any given time was not exceeded. The software in the program is supposed to take a 15 DAY rolling average and trigger an alert; apparently this did not happen either. The system broke down and needs to be looked at.
A Maintenance Technician reported an oil leak and significant oil consumption without apparent notice by other Maintenance or Company Personnel.  He noted that the oil tracking program is not identifying the elevated consumption.