Answer
If its sudden increase, likely due to leakage in fuel system.
To systematically diagnose an unexplained spike in Specific Fuel Oil Consumption (SFOC):
Combustion & Injection Parameters: Take indicator cards or performance profiles using an electronic cylinder pressure programmer. Check maximum combustion pressure (Pmax), compression pressure (Pcomp), and expansion curves. Low Pmax indicates late fuel injection timing, worn fuel pump plungers, or leaking fuel valves.
Air Supply Side: Check the turbocharger RPM, scavenge air pressure, and air cooler pressure drops . Worn turbocharger nozzles or a fouled air cooler reduces air mass flow, leading to incomplete combustion and high exhaust temperatures.
Fuel Quality: Cross-verify the latest bunker lab analysis report for the Lower Calorific Value (LCV) of the fuel oil. A lower LCV naturally demands a higher volume throughput to achieve identical kilowatt output.
External Factors: Review bridge data for hull slip, fouling indicators, and draft. A heavily fouled hull or damaged propeller blades will severely increase resistance, requiring more power and fuel for the same service speed.