Frequently asked
What is SFOC and what is a typical value?
Specific Fuel Oil Consumption — grams of fuel burned per kWh of shaft power. Typical SFOC for a modern two-stroke crosshead at ISO conditions is 165–175 g/kWh; medium-speed four-stroke runs 185–200 g/kWh. SFOC rises in poor weather, with biofouling, in shallow water (squat), and at off-design speed. The shop trial value on the engine certificate is the lowest you should expect; in service, plan on 5–10% higher.
How do I check a bunker invoice against the bunker delivery note?
Compare the BDN volume × density at the BDN reference temperature against the agreed quantity. The MARPOL bunker sample (Annex VI Reg. 18.8.1) is the legal evidence. If the in-line metered volume on board does not match the BDN, raise a Letter of Protest immediately and join the joint sample seal. Typical short-bunker findings are density misstatement and water content above ISO 8217 limits.
How do I estimate range from bunker tonnes?
Range (nm) = Bunkers (tonnes) × 1,000,000 / (SFOC × shaft power × 24 / speed). For a 60 t/day vessel at 14 knots, every 100 t of bunkers gives roughly 560 nm. Add a 10–20% reserve for weather routing, port contingency, and ECA fuel switching.
Why is bunker price quoted in USD/MT?
Industry convention is USD per metric tonne. Convert to USD/litre by dividing by 1,000 / density (so for VLSFO at 0.95 t/m³: USD/litre = USD/MT × 0.95 / 1,000). Density depends on grade and supplier; ISO 8217 specifies maximum density (typically 0.991 for RMG 380) but the actual delivery is on the BDN.
Fuel consumption & bunker calculator
Estimate daily fuel burn, range, total cost, and cost per nautical mile from bunker tonnes, SFOC, shaft power, and speed. Use to sanity-check a bunker invoice against expected consumption, plan voyage fuel reserves, and compare bunker prices on a per-mile basis. ISO 8217 grade selection affects density; default 0.95 is typical for VLSFO.
VLSFO ~0.95, MGO ~0.85.
Two-stroke 165–175, four-stroke 185–200.
Result
- Total cost
- USD 55,000
- Volume
- 105,263 L
- Daily burn
- 33.6 t/d
- Days at sea
- 3.0
- Range
- 1,000 nm
- Cost per nm
- USD 55.00
Add 10–20% reserve for weather routing, port contingency, and ECA fuel switching. SFOC quoted on the engine shop trial is the lowest practicable; in-service consumption is typically 5–10% higher due to wear, biofouling, and operating off-design.
Sources: ISO 8217 (marine fuels), MARPOL Annex VI Reg. 18 (bunker delivery note), CIMAC SFOC reference data; see also ISO 8217, bunker sample, CII rating, CII calculator.