At what altitude can a piston engine typically operate?

Piston engines can typically operate effectively up to around 12,000 feet, which is a range where the engine can still produce sufficient power due to the denser air in lower altitudes. At higher altitudes, the air becomes less dense, which affects the engine's performance because piston engines rely on atmospheric pressure for proper operation. While some piston engines may function at altitudes beyond this level, performance often decreases significantly, and it becomes challenging for the engine to maintain optimal operation. The 12,000-foot mark represents a practical limit where many light general aviation aircraft that utilize piston engines can operate efficiently without a major loss in power or climb rate.