What is the danger of running the engine too lean?

Running an engine too lean means that there is insufficient fuel mixed with the air entering the engine, which can lead to increased combustion temperatures. This can result in engine overheating, as the fuel serves not only to combust but also to help regulate temperature. When the mixture is too lean, the combustion process becomes more efficient but at a cost. The increased heat can lead to detonation—a condition where the fuel ignites prematurely, causing a rapid increase in pressure within the combustion chamber. This can damage engine components, lead to loss of performance, and in severe cases, result in engine failure.

Improperly managing fuel mixture can thus pose significant dangers, particularly in piston engines commonly used in private piloting. Ensuring the correct fuel-air mixture is crucial for optimal engine performance, temperature management, and overall reliability.