SFOC Tool: Marine Engine Fuel Consumption & Efficiency

SFOC • Fuel Rate • Brake Power • Engine Load • LCV Normalization • Thermal Efficiency • OEM Curve • Fuel Penalty

SFOC Tool: Marine Engine Fuel Consumption & Efficiency

Calculate measured specific fuel oil consumption, normalize it to a reference fuel energy basis, compare it with an OEM/shop-trial target and quantify the fuel and cost penalty. Simple mode handles one operating point quickly. Advanced builds a multi-load performance curve with brake-power or generator-output measurement, LCV normalization, thermal efficiency, annual operating profile and load-point diagnostics.

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Need much more depth? Click Advanced above.Advanced adds multiple load points, brake-power vs generator-output measurement, generator efficiency, operating-share weighting, OEM/reference curves, load-specific LCV, annual penalty by load, performance plots and measurement-readiness checks.

Fast9 primary inputs

Core answerActual vs reference SFOC

UsefulFuel + cost penalty quantified

Fast Engine Efficiency Screen

Use actual brake/shaft power, not nameplate power. The reference SFOC should be for the same engine, tuning/emissions mode and a comparable load point whenever possible.

Engine application

Engine MCR / rated brake powerkW.

Measured brake / shaft powerkW during the fuel measurement.

Fuel consumed during testkg.

Measurement durationminutes.

Actual fuel LCVMJ/kg from BDN / laboratory data.

Reference / OEM SFOCg/kWh on the reference LCV basis.

Fuel priceselected currency / tonne.

Annual hours at this conditionhours/year for penalty estimate.

Engine & Comparison Basis

Engine application

MCR / rated brake powerkW.

Reference LCVMJ/kg. 42.70 is common in OEM liquid-fuel SFOC declarations.

Reference source

Fuel price

Annual engine operating hours

Load-Point Test Register

Each row is one steady operating point. For electrical-output rows, brake power = electrical output ÷ generator efficiency. Operating share is used for annualized fuel and penalty estimates; it does not need to total 100% if only part of the operating profile is being assessed.

Power basis	Measured kW	Gen eff %	Fuel used kg	Test min	Actual LCV	Reference SFOC	Operating share %

Measurement Readiness

Engine operating point stableLoad, speed and fuel condition were reasonably steady during measurement. Power measurement basis verifiedShaft/torque, engine output or generator output method is understood. Fuel mass measurement verifiedFlowmeter, weighing or tank-measurement basis checked. Fuel LCV source verifiedBDN / laboratory energy content and units confirmed. Reference boundary matchedDriven pumps / auxiliaries are treated consistently with the OEM or baseline figure. Reference tuning / emissions mode matchedNOx mode, engine tuning and configuration are comparable. Ambient / test conditions reviewedAny formal ISO/OEM correction remains a separate documented step. Measurement instruments checkedCalibration / accuracy is suitable for the intended comparison.

Engineering limitation: measured SFOC is only as good as the power, fuel-mass, time and fuel-energy measurements behind it. LCV normalization in this tool is an energy-basis comparison only and is not presented as a full ISO/OEM correction to standard reference conditions. Use the engine maker’s approved performance-correction method and test boundary for contractual guarantees, warranty evaluation or formal acceptance testing.

Current methodology context: SFOC is fuel mass consumed per unit of useful engine energy output, normally expressed in g/kWh. ISO 3046-1:2002 remains the published standard for declarations of power and fuel consumption for reciprocating engines, although a replacement DIS is under development. ISO 15550:2016 provides general requirements for engine power and fuel-consumption determination, and ISO 3046-3:2006, reconfirmed in 2025, covers performance-test measurement techniques for comparison with manufacturer values. Current OEM data commonly states liquid-fuel SFOC at defined ISO conditions and a stated LCV; Wärtsilä, for example, publishes liquid-fuel SFOC using an LCV of 42.7 MJ/kg. Always use the applicable engine-specific maker data for the final reference curve.

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