Specific Fuel Consumption (S.F.C.) can be defined as?

Specific Fuel Consumption (S.F.C.) is defined as the weight of fuel used per unit of power produced per unit of time, typically expressed in terms of pounds of fuel per horsepower-hour or kilograms per kilowatt-hour. This definition effectively quantifies how efficiently an engine converts fuel into usable power; a lower S.F.C. indicates a more efficient engine that requires less fuel to produce the same amount of power.

Focusing on this definition, the other options do not accurately represent what S.F.C. measures. The first option addresses compatibility with fuel types, which is unrelated to the efficiency aspect of fuel consumption. The third option inaccurately states that S.F.C. increases with thermal efficiency; this contradicts the relationship between efficiency and fuel consumption, as higher thermal efficiency generally leads to lower S.F.C. The fourth option is mistaken as well; if engine efficiency improves, we would expect S.F.C. to decrease, indicating better performance with less fuel use. Thus, the correct choice is the one that precisely describes the metric of fuel consumption related to power output.