Why is tetraethyl lead added to aviation gasoline?

Tetraethyl lead is added to aviation gasoline primarily to increase the critical pressure and temperature of the fuel. By doing so, it enhances the fuel's octane rating, allowing for higher compression ratios in aircraft engines. This improvement is crucial because it helps prevent engine knocking, which can lead to reduced performance and potential engine damage.

The presence of tetraethyl lead in gasoline allows for more efficient combustion at the high temperatures and pressures typical of aviation engines, ensuring that the engine operates smoothly and effectively under demanding flight conditions. Higher octane fuels are also necessary to optimize performance and reliability in high-performance aircraft engines.

While other choices mention features related to emissions or combustion efficiency, tetraethyl lead's primary role in aviation fuel is tied to its ability to improve octane rating and support engine design, which ultimately links back to its effects on pressure and temperature in the combustion process.