Private Pilot Private Exam

Which type of fuel can be substituted if the recommended octane is unavailable?

1. A fuel of lower octane rating

2. The same octane aviation gas

3. Aviation gas with the next higher octane rating

4. A petroleum-based fuel

The correct answer is: Aviation gas with the next higher octane rating

Choosing aviation fuel with the next higher octane rating is the correct approach when the recommended octane is unavailable because it helps to ensure that the engine operates safely and efficiently. Higher octane fuels can better withstand the pressures and temperatures found in aircraft engines, which is crucial for preventing issues like knocking or pre-ignition that can lead to engine damage. Using a fuel with the next higher octane rating maintains enough resilience against detonation while still being compatible with the engine's design. It is essential for pilots to adhere to the manufacturer's specifications and recommendations to ensure optimal performance and safety during flight operations. The other options, such as selecting a lower octane rating, might lead to performance issues or damage to the engine. Similarly, using an improper fuel type, like a petroleum-based fuel, could compromise the integrity of fuel systems, leading to potential engine failure. Thus, adhering to the guidance of using aviation gas with the next higher rating provides a reasonable compromise when optimal fuel is unavailable.