G1 ARR INTO OAK EXPERIENCED A WAKE ENCOUNTER FROM PRECEDING B737 AT FL260.

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IT WAS A BEAUTIFUL DAY TO FLY. OUR TRIP FROM SNA-OAK WAS THE LAST OF A 2 LEG TRIP THAT DAY (FIRST FROM EGE-SNA). WE LAUNCHED RIGHT ON TIME FROM SNA AND QUICKLY CLBED TO FL310. FLT PLAN: CHANL1 DEP; GMN TRANSITION PXN2 ARR OAK. WE ARE USED TO COMPETING ON THE AIRWAY SPACE WITH ACR'S. SEVERAL ACFT RPTED TURB AT FL280; AND THE ACR Y IN FRONT OF US WAS ONE OF THEM. AS SUCH; HE REQUESTED AND WAS GRANTED A SLOWER THAN NORMAL SPD OF MACH .72. OUR CRUISE SPD TODAY WAS MACH .80. ANOTHER ACR Z BEHIND US COMPLAINED OF BUMPS AT LOWER ALTS AND I VOLUNTEERED THAT THE RIDE AT FL310 WAS FINE; SO ATC CLBED THE TFC BEHIND US TO FL310 AS WELL. AS WE PASSED GMN; I COULD SEE THE SLOWER; LOWER ACR Y JET IN FRONT OF US. THERE WAS ALMOST NO WIND THIS DAY; THE FMS RPTED 6 KTS. THE TCASII UNIT SHOWED US GAINING ON HIM QUITE QUICKLY. I KNEW THIS WOULD BE A CONFLICT AS WE WOULD BOTH BE DSNDING FOR OAK AND I WASN'T QUITE SURE HOW ATC WAS PLANNING ON SORTING OUT THE DSCNT. AS IT TURNED OUT; ABOUT 50 NM ON PXN; ATC SAW THE PROB AND SLOWED US DOWN TO MACH .75; ASKED THE JET TO SPD UP TO 'MAX FORWARD' AND WAITED. ACR Y CREPT FROM 2 NM IN FRONT OF US TO 5 NM. THEN WE WERE BOTH ISSUED DSCNTS TO MAKE STAR XING RESTRS (BORED INTXN AT 10000 FT; 250 KTS). THE JET STARTED DOWN; AND SO DID WE. AT FL260; WE FOUND HIS WAKE: WITH THE AUTOPLT ENGAGED; THE AIRPLANE SUDDENLY ROLLED 15 DEGS R. I DISCONNECTED THE AUTOPLT; COUNTERED THE ROLL AND CLBED SLIGHTLY (400 FT); THINKING WE WERE IN HIS WAKE AND COULD CLB ABOVE IT. OUT OF 200 FT; THE ROLLING AND BUCKING TREND INSTANTLY STOPPED. MY FO RESPONDED ON THE RADIO THAT WE HAD CLBED DUE TO WAKE ENCOUNTER AND WE CONTINUED DOWN AT A SLOWER RATE. I WOULD ESTIMATE ACR Y JET WAS 6-8 NM IN FRONT OF US AT THIS POINT. AFTER XING PXN VOR; WE CONTINUED DOWN AND ENCOUNTERED IT AGAIN AT FL180. THIS TIME; I OFFSET SLIGHTLY TO THE R OFF COURSE TO AVOID ANY FURTHER ENCOUNTER. AS WE SWITCHED TO NORCAL APCH; ATC QUERIED; 'I DON'T KNOW HOW YOU ARE NAVING; BUT YOU SEEM TO BE ABOUT 1 MI E OF CTRLINE.' I RESPONDED THAT WE WERE EXACTLY 1 NM E OF CTRLINE (PER PROGRAMMING) DUE TO WAKE TURB WITH THE JET PRECEDING US INTO OAK. THERE WAS SILENCE; THEN ATC ASKED; 'NOT IN MY SECTOR WAS IT?' NO; IT WAS WITH CTR; PRIOR TO HIS HANDING US OFF TO YOU. WE WERE VECTORED ONTO FINAL FOR RWY 27R; WHILE ACR Y JET WENT TO RWY 29 AND NO FURTHER INCIDENTS WERE ENCOUNTERED OR MENTIONED. LESSONS: WATCH OUT IN SMOOTH AIR FOR RELATIVELY STABLE VORTEX GENERATION AND TRY TO MAINTAIN 10 NM IN-TRAIL; VERSUS 5 NM OFFERED BY ATC; EVEN IN A 50000 LB AIRPLANE!