What are possible outcomes of using a lower grade of avgas than specified?

Using a lower grade of aviation gasoline (avgas) than specified can lead to several detrimental outcomes for the engine's performance and integrity. Specifically, using a lower octane fuel can cause "knocking" or detonation, which is a premature ignition of the fuel-air mixture in the engine cylinders. This can result in increased stress on engine components and potentially lead to engine damage over time.

In addition to the risk of engine damage, a lower grade of avgas can also cause a loss of power. The engine is designed to operate optimally with fuel that meets specific octane ratings, which help prevent knocking and ensure efficient combustion. Using fuel with a lower octane rating can hinder the engine's ability to perform at its best, resulting in decreased power output.

Thus, the use of a lower grade of avgas than specified increases the likelihood of engine damage and loss of power, making it crucial for aircraft operators to adhere to the manufacturer's fuel specifications to maintain both performance and safety.