Answer
Although 0.45% water by volume sits strictly within the engine maker's acceptable baseline limit 0.5%, it is an elevated, borderline level that requires proactive technical intervention from the Chief Engineer to halt progressive damage.
Immediate Engineering Action Plan
Identify the Source (Freshwater vs. Saltwater): Run an onboard Silver Nitrate (AgNO_3) test on an oil sample drawn from the main engine drain tank.
If a milky-white precipitate forms, it confirms saltwater ingress (suspect a leaking lube oil cooler).
If no reaction occurs, it confirms freshwater ingress (suspect a leaking piston cooling telescopic pipe, cracked cylinder liner seal, or jacket water boundary leak).
Optimize Purifier Operations:
Set up the lube oil purifier strictly in separation mode (fitted with the precisely sized gravity disc matched to the oil's elevated density).
Reduce the purifier throughput flow rate to one-third (33%) of its maximum rated volumetric capacity to maximize retention time inside the bowl.
Maintain the separation heating temperature tightly at 85C - 90C to reduce viscosity and accelerate the phase-separation of water.
Continuous Monitoring Loop: Increase the frequency of shipboard water-in-oil tests using the onboard chemical test kit to every 24 hours. Monitor the main engine crankcase oil mist detector (OMD) readings and bearing temperature telemetry closely.