A 4-stroke engine is a mechanical system that turns burning fuel into motion through four steps: intake, compression, power, and exhaust. Inside a metal cylinder, a piston slides up and down to pull in air and fuel, squeeze the mixture, capture the force of a spark plug ignition, and push out waste gas. This up-and-down movement turns a crankshaft, converting linear energy into the rotational power needed to turn wheels or blades. Because they keep engine oil separate from the fuel, 4-stroke engines run smoothly, produce clean exhaust, and offer great fuel efficiency.