As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENG OIL LOSS IN 2 HOURS INDICATION WENT FROM 11 DOWN TO3. ABOUT 20 MINS LATER DROPPED TO 2. CHANGING THROTTLE SETTING AND EICAS COMPUTERS, NO HELP. RETURNING TO JFK. OPENED NR 1 ENG PRESSURIZED GEARBOX THROUGH BREATHER. FOUND LEAKING FROM IDG CARBON SEAL NEEDS NEW CARBON SEAL. REMOVED AND REPLACED IDG CARBON SEAL PER AMM. RAN ENG AT T/O PWR. PERFORMED ENG LEAK CK. NO LEAKS FOUND. IDG OPS OK. CHIP DETECTORS OK.