The Basics
The purpose of a gasoline car engine is to convert gasoline into motion so that your car can move. Currently the easiest way to create motion from gasoline is to burn the gasoline inside an engine. Therefore, a car engine is an internal combustion engine -- combustion takes place internally. Two things to note:
  • There are different kinds of internal combustion engines. Diesel engines are one form and gas turbine engines are another. See also the articles on Hemi engines, rotary engines and two-stroke engines. Each has its own advantages and disadvantages.

  • There is such a thing as an external combustion engine. A steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine. Internal combustion is a lot more efficient (takes less fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we don't see any cars from Ford and GM using steam engines.

Inside a typical car engine

Almost all cars today use a reciprocating internal combustion engine because this engine is:

  • Relatively efficient (compared to an external combustion engine)
  • Relatively inexpensive (compared to a gas turbine)
  • Relatively easy to refuel (compared to an electric car)
These advantages beat any other existing technology for moving a car around.