A B767 ENG HAD EXCESSIVE OIL CONSUMPTION IN FLT. THE CREW DIVERTED TO A NEARBY ENROUTE ARPT WHILE ENG OIL REMAINED AVAILABLE.

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LAST NIGHT I WAS SCHEDULED TO FLY FROM ZZZ TO ZZZZ. DURING MY PREFLT REVIEW OF THE ACFT LOGBOOK; I NOTICED MANY ENTRIES FOR OIL SVC ON THE L ENG AND THAT THERE WAS A MAINT WATCH FOR OIL CONSUMPTION AS WELL. THERE WERE NO SIGNS OF AN OIL LEAK DURING THE PREFLT BY MY RELIEF PLT AND THE CONSUMPTION SEEMED TO BE INTERNAL USE AND UNDER CTL; SO I ACCEPTED THE ACFT AND WE DEPARTED AS SCHEDULED. WE HAD BOTH ENGS FULL OF OIL AT 21 QUARTS WHEN WE LEFT THE GATE AND BOTH WERE NORMAL AFTER ENG START AND WHEN WE REACHED THE TKOF POS. AFTER LEVELOFF AT OUR CRUISE ALT; THE L ENG SHOWED 1 QUART LESS THAN THE R ENG; SO I STARTED TO MONITOR THE OIL LEVELS CLOSELY. AFTER ABOUT 90 MINS OF FLT WE WERE DOWN TO 14 QUARTS OF OIL IN THE L ENG AND WE REALIZED THAT IF THE CONSUMPTION CONTINUED WE WOULD NOT HAVE ENOUGH OIL TO REACH ZZZZ. I DECIDED TO DIVERT WHEN THE OIL LEVEL REACHED 13 QUARTS AND CONTACTED DISPATCH TO COORDINATE A SUITABLE ALTERNATE. WE DECIDED TO RETURN TO ZZZ AND TURNED THE ACFT AROUND BACK TO THE N. THE OIL CONSUMPTION INCREASED AT THIS POINT AND TO AVOID AN ENG SHUTDOWN I CHANGED THE LNDG ARPT TO ZZZ2. WE DECLARED AN EMER; FLEW DIRECT TO ZZZ2. THE OIL HAD DROPPED TO 5 QUARTS AND I DECIDED IT WAS BETTER TO LAND OVERWT AND GET THE ACFT SAFETY ON THE GND THAN TRY TO CIRCLE AND DUMP FUEL. WE REQUESTED CFR EQUIP TO STAND BY FOR LNDG AND MADE A NORMAL APCH AND LNDG. THE OIL LEVEL WAS 4 QUARTS ON LNDG AND THE LNDG WAS SOFT WITH A SINK RATE NEAR 0 FPM. ZZZ2 MAINT FOUND AN OIL LINE LOOSE ON THE L ENG AND CORRECTED THE PROB AND COMPLETED AN OVERWT LNDG INSPECTION AND WE THEN CONTINUED THE FLT TO ZZZ1 WITH NO FURTHER PROBS.