The statement 'A negative horsepower run measures parasitic loss in the vehicle' is true.

• A. Not Sure
• B. Not Applicable
• C. True
• D. False

Answer: (C)

Parasitic losses are the horsepower the engine spends on things that don’t move the car, like the alternator, water pump, oil pump, power steering, cooling fans, and other accessories. A negative horsepower run is a way to quantify exactly how much power those non-propulsive loads are drawing from the engine. On a dynamometer or test setup, you measure the engine’s output while these accessories are running; the power that shows up as negative (or as a deficit from the engine’s gross output) represents the parasitic loss. So, the statement is true because that negative power reading is effectively the measure of energy being spent on those parasitic loads.