MLG FLC RETURNS TO LAX FOR MAINT WITH ENG OIL FILTER CLOGGED LIGHT.

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DEPARTED LAX FOR BNA. WHEN CLBING THROUGH FL200; THE L ENG OIL STRAINER CLOGGING LIGHT CAME ON. LEVELED OFF AND COMPLETED RED BOOK ITEM 'REDUCE THRUST.' LIGHT STAYED ON; SO CALLED MAINT. ALSO CALLED DISPATCH. CONTINUED E IN EVENT WE COULD RESOLVE PROB AND STILL MAKE BNA. AFTER LENGTHY WAIT FOR MAINT CTL TO RESPOND TO LAX MAINT WE WERE 150 MI FROM PHX. ASKED DISPATCH HOW THEY FELT ABOUT LNDG AT PHX. LAX MAINT SAID IT WOULD TAKE 3-5 HRS TO CHANGE FILTER AND OIL. HELD OVER PARKER AS WE STILL HAD 2 HRS OF FUEL TO BURN OFF TO GET DOWN TO 130000 LBS. SINCE WE COULD NO LONGER SAFELY MAKE BNA AND MAINT CTL FINALLY DECIDED NOT TO HAVE US TRY PHX OR DFW AS THEY FELT THE BEST THING TO DO WAS TO RETURN TO LAX; DISPATCH ADVISED US TO RETURN TO LAX. IN THE MEANTIME; LAX TWR TOOK IT UPON THEMSELVES TO DECLARE AN EMER FOR US AS THEY THOUGHT WE HAD LOST AN ENG. WITH THE CONCURRENCE OF MAINT CTL AND DISPATCH; WE LANDED OVERWT AT 137500 LBS AT LAX WITH A SOFT LNDG TO TRY TO ACCOMMODATE PAX CONNECTIONS TO BNA. ALL HINTS FROM MAINT CTL AND LAX MAINT SEEMED TO INDICATE THEY WANTED US TO RETURN TO LAX ASAP WITH OUR CURRENT ENG SIT.