What does the number 100 signify in 100LL aviation gasoline?

The number 100 in 100LL aviation gasoline refers to the lean mixture performance number, which indicates the fuel’s octane rating. Specifically, it suggests that the fuel has an octane rating of 100 when tested under lean conditions. This rating is essential in aviation as it helps to prevent engine knocking and allows for efficient performance and safety in high-performance aircraft engines.

The term "LL" signifies "low lead," indicating that this type of aviation gasoline contains a reduced level of lead compared to older formulations, making it more environmentally friendly and in line with regulatory standards. The octane rating is crucial for aircraft engines, which often operate at higher pressures and temperatures, necessitating a fuel that can withstand such conditions without detonation.

The other choices involve aspects that are not represented by the number 100 in this context. For instance, it is not related to the weight of the fuel, nor does it refer to the manufacturer or the maximum temperature limit of the fuel. Thus, understanding the significance of the octane rating is vital for the safe and efficient operation of aviation engines.