Efficiency
A concept closely related to the BTU or KWH potential of a given fuel is Engine Efficiency often called Thermal Efficiency in the case of internal combustion engines.
Generally speaking, an electrical motor is more efficient than an internal combustion engine at converting potential energy into work - turning the wheels that may move a car down the road.
A diesel cycle engine can be as high as 40% to 50% efficient at converting fuel into work, where a standard automotive gasoline engine will be about 25% to 30%.
The efficiency of converting a unit of fuel to rotation of the driving wheels, includes many points of friction (loss): Heat that goes out the exhaust pipe or through the engine block to the radiator. Friction inside the engine, happens along the cylinder walls, crank, cam and main bearings; plus drive chains or gears. Friction outside the engine, includes loads from the generator, power steering pump, power brake pump, A/C pump, transmission, differential and universal joints; plus rolling resistance of the pneumatic tires.
The MPG of a given vehicle starts with the thermal efficiency of the fuel and engine, less all of the above elements of friction.
Read more about this topic: Gasoline Gallon Equivalent
Famous quotes containing the word efficiency:
““Never hug and kiss your children! Mother love may make your children’s infancy unhappy and prevent them from pursuing a career or getting married!” That’s total hogwash, of course. But it shows on extreme example of what state-of-the-art “scientific” parenting was supposed to be in early twentieth-century America. After all, that was the heyday of efficiency experts, time-and-motion studies, and the like.”
—Lawrence Kutner (20th century)
“I’ll take fifty percent efficiency to get one hundred percent loyalty.”
—Samuel Goldwyn (1882–1974)
“Nothing comes to pass in nature, which can be set down to a flaw therein; for nature is always the same and everywhere one and the same in her efficiency and power of action; that is, nature’s laws and ordinances whereby all things come to pass and change from one form to another, are everywhere and always; so that there should be one and the same method of understanding the nature of all things whatsoever, namely, through nature’s universal laws and rules.”
—Baruch (Benedict)