A B757-200 CAPT RPTED THAT CONTRACT MAINT IN A FOREIGN COUNTRY WAS NOT PROFICIENT IN AN ENG CHK BEFORE DEP FROM ZZZZ WHICH MAY HAVE CONTRIBUTED TO AN ENG OIL PROB THAT CAUSED THE RPTR TO DIVERT TO BDA.

Narrative

AFTER A LENGTHY STRUGGLE; MAINT FINALLY INFORMED US; IN DETAIL; OF THE PROB WITH ACFT SINCE THERE WAS NOT A LOGBOOK ON THE ACFT WHEN WE ARRIVED. AFTER 2 CALLS TO DISPATCH WITH A PHONE PATCH TO B757 TECHNICIAN EACH TIME; I TOLD MAINT THAT THE ENG WAS GOING TO HAVE TO BE FURTHER INSPECTED; DESPITE THE FACT THAT MAINT INSISTED THAT THE 30 MIN TURN UP THEY HAD EARLIER DONE WOULD SUFFICE. ONCE THE CHK WAS ACCOMPLISHED; WE LEFT. THE FIRST HR OF THE FLT WAS UNEVENTFUL AND THEN THE R OIL QUANTITY BEGAN A STEADY DECLINE FROM 21 TO 15 IN ABOUT 35 MINS. AFTER A VERY LENGTHY ALGEBRAIC COMPUTATION WITH 23 COMPLEX VARIABLES; WE THREW AWAY THAT PAPERWORK SINCE NEITHER OF US WERE PROFICIENT IN ADDITION AND DECIDED THE REMAINING OIL WAS NOT GOING TO ALLOW US TO REACH EWR WITHOUT SHUTTING DOWN THE ENG OR BURNING IT UP. WE DIVERTED INTO BDA WITH 9 SHOWING ON THE GAUGE JUST BEFORE TOUCHDOWN. I DID NOT DECLARE AN EMER BECAUSE NEW YORK OCEANIC RESPONDED IMMEDIATELY WITH A CLRNC FROM HOLMA DIRECT TO BDA AND ZNY ON 128.5 HAD US IN RADAR AS SOON AS WE MADE THE TURN.