GA SMA LOST ENGINE OIL AT TOC. INSTRUCTOR PLT RETURNED TO DEP ARPT.

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NORMAL DAY (VFR) PERFORMED NORMAL PREFLT. FLT WAS INTENDED TO RECERTIFY ANOTHER PLT. LEFT DAVIS UNIVERSITY ARPT; CA; AND PROCEEDED TO BUCHANAN FIELD. ACFT HAD JUST COME OUT OF 100 HR INSPECTION. DEPARTED CONCORD. LEVELED OFF 3500'. CONTACTED TRAVIS APCH FOR RADAR SVC. STUDENT INITIATED CRUISE CHKLIST. I WATCHED AS SHE CONTINUED TO RUN THE CHKLIST. WHEN THE PROP CTL WAS RETARDED FOR DESIRED RPM; THE PROP RACED OUT OF CTL. MP WAS REDUCED AND AN ATTEMPT TO REGAIN SOME CTL ON PROP WITH PROP CTL. THE ATTEMPT WAS INEFFECTIVE. THE OIL PRESSURE GAUGE WAS JUST REACHING 0. OIL TEMP WAS NORMAL. I CONTACTED TRAVIS APCH AND INFORMED THEM OF ENG TROUBLE AND WOULD NEED TO LAND ON THE AIR BASE (I DECLARED AN EMER). I REASSESSED DISTANCE AND WIND CONDITIONS AND DECIDED ON CONCORD AS BEST CHOICE; INFORMED TRAVIS OF MY INTENTIONS AND TURNED BACK TOWARD CONCORD; SETTING UP MY GLIDE WITH ENG STILL RUNNING. APPROX 2 MINS PASSED AND I EXTENDED THE LNDG GEAR. APPROX 30 SECS LATER THE ENG BEGAN TO SHUDDER VIOLENTLY SO I SHUT DOWN THE ENG. I WAS INSTRUCTED TO CONTACT CONCORD TWR. CONTINUED GLIDE TO NORMAL (UNEVENTFUL) LNDG. LATER THE FIREMEN AND A MECH TOLD ME THEY DETECTED A FINGER TIGHT LINE CONNECTOR ON THE OIL COOLER LINE.