100LL is a type of aviation fuel specifically designed for piston-engine aircraft. The "100" indicates its octane rating, which helps prevent engine knocking, while "LL" stands for "low lead," meaning it contains a reduced amount of lead compared to older aviation fuels. This makes it safer for the environment and helps protect engine components. This fuel is commonly used in general aviation and is essential for many small aircraft. 100LL is typically blue in color, making it easily identifiable at airports. Pilots and aircraft operators rely on this fuel for optimal performance and safety during flight.