HIGH ENG OIL CONSUMPTION CAUSES AN ACR WDB TO DIVERT LAND.

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ON 747 FLT WBOUND BTWN NULUK AND NINNA ON R220 AT FL350. DUE TO WHAT APPEARED TO BE AN IMPENDING SHUTDOWN OF #4 ENG DUE TO EXCESSIVE OIL CONSUMPTION; WE DECIDED TO GET A RERTE BACK ON R220 TO ANCHORAGE SINCE FUEL CONSUMPTION ON 3 ENGS MADE A CONTINUANCE TO NARITA UNACCEPTABLE AND DIVERSION ARPTS ALONG THE RTE WERE MUCH LESS SUITABLE THAN ANCHORAGE. WE DID NOT DECLARE AN EMER BECAUSE WE HAD NOT SHUT DOWN #4 ENG YET. WE REQUESTED A RERTE FROM ZAN VIA VHF. ZAN INFORMED US THAT WE COULD NOT REVERSE COURSE AT FL350 DUE TO TFC AND COULD NOT DSND ON TRACK; THEN REVERSE COURSE DUE TO TFC. WE SUGGESTED A DEV S OF TRACK; BUT THAT WOULD PUT US IN CONFLICT WITH TFC ON R220 AND THE NEXT RTE S. WE HAD CONVERGING TFC (ACR B 747) ON 517 CONVERTING INTO R220 AT NINNA. WE ASKED ZAN; OTHER THAN CONTINUING WBOUND ON R220; WHAT WOULD HE SUGGEST. HE SUGGESTED DEVIATE R; THEN DSND; THEN REVERSE DIRECTION. I MADE A 45 DEG R TURN RATHER THAN 90 DEGS SO AS TO STAY AHEAD OF ACR B. I HAD VISUAL CONTACT AND ACR B CONFIRMED VISUAL CONTACT AFTER BEING INFORMED BY CTR OF OUR INTENTIONS. STARTING THE DSCNT; I NOTICED ACR B GAINING ON US VIA VISUAL AND TCASII. I SHALLOWED THE DEV TO 30 DEGS TO STAY AHEAD. WE PASSED THROUGH ACR B'S ALT OF FL310 AT OVER 5 MI SEPARATION ON TCASII BUT THAT IS NOT THE PARAMETERS FOR TFC SEPARATION ON THE NOPAL. ACR B APPEARED TO MAKE A L TURN TO INCREASE SEPARATION. THERE WERE NO TA'S OR RA'S FROM THE TCASII. ONCE ESTABLISHED AT FL290; WE CONTINUED THE R TURN AND REESTABLISHED EBOUND ON R220 TO ANCHORAGE. TCASII WAS AN INVALUABLE TOOL TO BACK UP THE VISUAL SEPARATION.