In a four-stroke internal combustion engine, what are the four strokes in order?

The four-stroke cycle (Otto cycle, used in most gasoline car engines) operates in this sequence: (1) INTAKE — piston moves DOWN; intake valve OPEN, exhaust valve CLOSED; air-fuel mixture drawn into cylinder; (2) COMPRESSION — piston moves UP; both valves CLOSED; air-fuel mixture compressed to high pressure (8:1 to 12:1 compression ratio typical for gasoline, higher for high-performance); (3) POWER (combustion/expansion) — spark plug fires just before piston reaches top dead center; ignited mixture expands rapidly, forcing piston DOWN; this is the only stroke that produces power; (4) EXHAUST — piston moves UP; exhaust valve OPEN, intake CLOSED; burnt gases pushed out through exhaust port. Memory aid: 'Suck, Squeeze, Bang, Blow.' Each cylinder fires once every TWO crankshaft revolutions (the crankshaft turns 720° per complete cycle since each stroke = 180°). Multi-cylinder engines: cylinders fire in a specific sequence (firing order) staggered so power strokes overlap, providing smoother power. Common firing orders: 4-cylinder typically 1-3-4-2 or 1-2-4-3; V8 typically 1-8-4-3-6-5-7-2. CRANKSHAFT converts the up-down reciprocating motion of pistons into rotational motion. CAMSHAFT operates the valves; rotates at half crankshaft speed (one cam rotation per two crank rotations); driven by timing belt, chain, or gears. Two-stroke engines (older motorcycles, chainsaws, outboard motors) combine the four strokes into two using ports and crankcase compression — simpler but less efficient and more polluting. Diesel engines also four-stroke but use COMPRESSION IGNITION (no spark plug; high compression heats air enough to ignite injected fuel) — compression ratios 14:1 to 22:1.