What was found
#1 ENGINE TREND DATA SHOWS A 5 PSI SHIFT IN TAKE OFF AND CRUISE OIL PRESSURE. NOTE: CURRENT OIL PRESSURE REMAINS IN THE NORMAL N2 VERSUS OIL PRESSURE OPERATIONAL BAND. GROUNDED - YES. ACCOMPLISHED TSR STEP 1 & 2. OIL POP OUT INDICATOR NOT EXTENDED. NO DAMAGE TO OIL LINES FOUND, OIL TANK SCREEN HAD NO CONTAMINATION. REPLACED LUBE UNIT ON #1 ENGINE. OPTS CK GOOD, NO LEAKS NOTED. REF. B737-900 AMM 79-21-01. TSR CONFIRMS OIL PRESSURE INDICATION TO BE WITHIN PUBLISHED MANUAL LIMITS PER AMM 71-00-00-800-806-F00. TECH SERVICES WILL CONTINUE TO MONITOR THE OIL PRESSURE ON SUBSEQUENT FLIGHTS.