The servo cannot be oiled. Jaw squeak can occur when the cable ties that hold on the jaw are too tight, this can be fixed by lubing the holes that the tie goes through. Also, the wire that connects the jaw to the servo can rub on the skull. Carefully shave away enough so it no longer touches the skull.
WARNING: HYDRAULIC AND PNEUMATIC POWER SYSTEMS CAN FAIL THROUGH MISUSE, AGE OR MALFUNCTION. THE SYSTEM DESIGNER
IS WARNED TO CONSIDER THE FAILURE MODES OF ALL COMPONENTS USED IN THE DESIGN AND ENGINEERING OF ALL SYSTEMS AND TO PROVIDE ADEQUATE
SAFEGUARDS TO PREVENT PERSONAL INJURY OR DAMAGE TO EQUIPMENT IN THE EVENT OF SUCH FAILURES