What grades of aviation fuel may be used in the C172S Nav III and their respective colors?

The C172S Nav III is designed to use 100 LL aviation fuel, which is colored blue. This fuel type is a low-lead formulation that helps in reducing lead deposits and is a common choice for many piston aircraft engines. The inclusion of green-colored fuel, specifically 100 octane (which is no longer widely used), is sometimes mentioned in older literature, but for modern general aviation, the relevant fuel options primarily include 100 LL blue.

100 LL is specifically designed to meet the performance requirements of most piston engines, including those in the C172S, while ensuring good combustion characteristics and enhanced engine life. Therefore, while the reference to a green fuel option might lead to confusion, it is important to note that the modern standard for this aircraft is the blue 100 LL.

In the context of other fuel options, they do not align with the specifications required for the aircraft, and using fuels outside of the recommended types could lead to engine inefficiencies or damage. Therefore, understanding the correct fuel to be used is essential for safe flying and proper aircraft maintenance.