What was found
WHILE IN CLIMB POWER AT FL310 THE LEFT ENGINE VIBRATION INDICATOR TURNED AMBER AND WAS INDICATING 3.1. AT COMPLETION OF THE CLIMB TO FL390 POWER WAS REDUCED TO 95.7 AND THE VIBRATION INDICATOR WAS STILL AMBER INDICATING 2.7. WHEN POWER WAS REDUCED TO 89.0 THE LEFT ENGINE INDICATED 2.3 VIBRATION VS. 1.2 FOR THE RIGHT ENGINE(NORMAL.). THERE WAS NO COMPRESSOR STALL HEARD AND THE SYNC REMAINED ON N1 THE ENTIRE TIME. CORRECTIVE ACTION: AS PER MCC AND GE REQUEST LUBED BOTH LH AND RH ENG FAN BLADES (SEE STEP 3.2.2 FOR WORK PERFORMED). PREPPED AND FUELED AIRCRAFT. PERFORMED IDLE RUN CHECK AND TAXIED AIRCRAFT TO THE RUN UP PAD. PERFORMED SEVERAL ENGINE RUNS AND TAXIED BACK. VIBRATION CHECK AT MAX POWER FOR LH ENG 0.3, RH 0.6. OPS CHECK GOOD. WORK DONE PER 71-00-00.