Aux. Engine: Low Lubricating Oil Pressure Or Drop in Pressure during operation.

Reasons & Countermeasures:
1. Low lube oil level in the tank (below lower limit)
Countermeasure: Replenish.

2. Improper oil viscosity.
Countermeasure: Replace.

3. Clogged lube oil filter (pump suction side).
Countermeasure: clean it.

4. Air sucked from inlet side (due to: *damaged piping or *non air-tight joint).
Countermeasure: maintenance/ replacement.

5. Leak from or damage to oil piping (discharge side).
Countermeasure: maintenance/ replacement.

6. Defective Lubricating Oil Pump
(*sticking of safety valve/broken spring
*wear of pump gear
*wear of Bearings)
Countermeasure: maintenance/ replacement.

7. Defective relief valve.
Countermeasure: maintenance/ replacement.

8. Damaged cooling water piping in Lubricating oil cooler.
Countermeasure: maintenance.

9. Wear of Bearings.
Countermeasure: maintenance/replacement.

#'Drop in Pressure during operation' may even happen due to 'High Lubricating oil temperature'..
(Refer 'High L.O. Temp' Defects & Troubleshooting)