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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.
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.
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.
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.
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.
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.