Answer
As Chief Engineer, I would not immediately assume an engine problem. First I will establish whether the increase is genuine.
1. Immediate Data Verification & Validation
- Verify Measurement Accuracy: Cross-check mass flowmeter readings against manual sounding/ullage calculations of settling and service tanks.
- Density & Temperature Corrections: Ensure Volume Correction Factors ($VCF$) and fuel density conversions match the current bunkered fuel batch.
- Isolate Fuel System Leaks: Inspect fuel oil supply, booster pumps, high-pressure fuel pipes, and return lines for physical leaks or leaking safety relief valves.
First eliminate a measurement/accounting error.
2. Compare operating conditions
Check whether:
- Ship speed increased
- Main engine RPM/load increased
- Draft/displacement increased
- Trim changed
- Bad weather/head sea
- Strong adverse current
- Shallow water
- Increased auxiliary load
If power demand has increased, higher consumption may be perfectly explainable.
3. Check main-engine performance
Take and compare performance readings against:
- Previous good readings
- Sea-trial/shop-trial data
- Sister-cylinder performance
- Manufacturer's data
4. Check combustion parameters
Look particularly for uneven exhaust temperatures and cylinder pressures.
5. Check air side / turbocharger
Poor air supply means poorer combustion and higher fuel consumption for the same power.
6. Check fuel quality
Check latest bunker/analysis report for:
- Density
- Viscosity
- Net calorific value
- Water
- Cat fines
- Compatibility
A fuel having a lower calorific value can cause an apparent increase in tonnes/day even though the energy delivered to the engine is similar.
7. Check hull and propeller
If engine performance is normal but fuel consumption is high, suspect:
- Hull fouling
- Propeller fouling
- Propeller damage
- Increased hull resistance
A useful comparison is:
Same RPM requiring higher power/fuel than historical clean-hull condition → investigate hull/propeller resistance.