I know gasoline is used for heating the air particles, but is that all it's used for? I'm new to this stuff and now I'm learning some of the energy is used for transporting the gas into the combustion chamber. Maybe I heard wrong. But my question is, Is gasoline only used for heating the air particles in the power stage, or do it have another use in the engine?

  • For those who are voting to close as "off-topic", this sure seems related to the ICE from my point of view. To the OP, maybe you can broaden your question a little bit? Help us to understand exactly what you're getting at? BTW, welcome to the site! We're glad you're here. Jan 26, 2017 at 16:06
  • Better? Sorry I'm new to learning this stuff and information is all of the place.
    – DeusIIXII
    Jan 26, 2017 at 16:15

1 Answer 1


An internal combustion engine is a type of heat engine as defined by the Carnot Cycle, specifically a gasoline engine uses the Otto Cycle.

In essence gasoline is burned in the cylinders, releasing heat and creating a large volume of hot gas which, as it is confined in the combustion chamber is under significant pressure. It is this pressure which forces the piston down and produces mechanical work.

In all engines some of the work produced will be used to drive ancillary processes which use of energy but are still essential for the operation of the engine, for example :

  • Induction : sucking air into the cylinder on each induction stroke requires some energy (although turbochargers can achieve this with waste energy from the exhaust).
  • Powering electrical systems such as ignition and starter motor.
  • Fuel, oil and coolant pumps
  • Operating valves and fuel injectors
  • Plus various other demands from the vehicle as a whole such as electrical power for lights etc.

Of course not all of the heat produced by combustion can be extracted as mechanical work and some is dumped directly via the exhaust (although turbochargers can extract additional energy form the exhaust) and some is shed by the cooling system via the radiator.

So in a gasoline engine providing hot combustion products which act as a working fluid is pretty much the parts of the inducted air (mostly nitrogen) plus the various products of the reaction between gasoline and oxygen, in theory this will be carbon dioxide and water vapour but in practice various other products including nitrogen oxides and carbon monoxide are produced as well. So strictly the fuel does produce some of the exhaust gasses directly as well as heating the air already in the cylinder.

In some engine types, notable 2-stroke engines the fuel also has a lubrication function and diesel fuel provides its own lubrication for the fuel injection system.

Fuels will also have various additives to control their combustion properties.

Historically some vehicles have used liquid fuel for cabin heating, but this is now long since obsolete.

  • Actually, all vehicles use liquid fuel for cabin heating! The cabin heat comes from the engine heat via the cooling system, and indeed the engine heat comes from liquid fuel. The need for heat is one of the reasons the internal combustion engine occasionally runs in a hybrid electric vehicle when driven at cold temperatures, even though the battery could supply traction power. Of course, some auxiliary heaters like mirror/rear window/windscreen heaters and seat heaters can be powered electrically.
    – juhist
    Jan 27, 2017 at 20:20

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