How does a gasoline engine turn burning fuel into motion?

Inside a gasoline engine, fuel releases energy by burning with oxygen. The hot gas pushes a piston: a close-fitting moving part inside a cylinder. A connecting rod joins the piston to a crankshaft. As the crankshaft turns, the piston moves down and up. The engine organizes this movement into a repeating four-stroke cycle.

First comes intake. The inlet valve opens while the piston moves down, allowing a fresh charge into the cylinder. Fuel may already be mixed with the air or may be injected separately. Next comes compression. The valves close and the piston rises, squeezing the trapped charge into a smaller space. A spark near the end of compression starts combustion.

The burning mixture becomes hot, high-pressure gas. During the power stroke, that gas pushes the piston down, transferring energy through the connecting rod to the turning crankshaft. Then the exhaust valve opens. The rising piston pushes spent gas out, making room for the next intake. The cylinder is ready to repeat the sequence.

Four strokes take two complete turns of the crankshaft, with one power stroke in each cylinder per cycle. Other cylinders and the rotating flywheel help carry the motion through the remaining strokes. The illustration separates the stages clearly; real engines overlap valve events and carefully adjust spark timing. Burning fuel supplies the energy, while the mechanism turns repeating gas pushes into rotation.