BSFC, or brake specific fuel consumption, refers to the fuel efficiency of a reciprocating, or piston-type, engine. The BSFC expresses the relationship between the power an engine produces and the fuel that it needs to produce that power. Understanding BSFC can help you decide whether or not to purchase a vehicle based on its fuel efficiency. The more fuel efficient your engine is, the less you will have to spend at the gas pump.

Find out the horsepower produced by your engine along with the pounds of gasoline used per hour. You may have to consult the manufacturer or the dealership to obtain this information.

Divide the pounds of gas used per hour by the horsepower that is produced.

Use the following example equation as a reference for your calculations: An engine produces 200 horsepower while consuming 36.3kg. of gasoline in an hour. Therefore, 80 divided by 200 would equal a BSFC of 0.4.