What was found
DIVERTED TO PHX DUE TO NUMBER 1 ENGINE OIL PSI DROPPING TO YELLOW RANGE, APPROX 20 PSI. AIRCRAFT LANDED WITHOUT INCIDENT. PERFORMED ENGINE RUN PER BOEING M/M, OIL PRESSURE AND QUANTITY REMAINED IN NORMAL RANGE. CHECKED METAL CHIP DETECTORS AND FILTERS, PERFORMED ENGINE RUN A SECOND TIME, ALL NORMAL.