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Aircraft systems and instrumentsQuestion 655 of 934

What does a higher AVGAS grade mean?

  1. The fuel has less lead and burns cleaner
  2. The fuel ignites at a lower temperature in the cylinder
  3. The fuel has a lower octane rating and more lead
  4. The fuel resists detonation at higher pressure
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Correct answer: The fuel resists detonation at higher pressure

Higher grades are used in higher-compression engines. They ignite at higher temperatures, but not prematurely.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Fuel Systems — Fuel Grades, page 187

Practice aircraft systems and instruments

Questions last reviewed: 18 October 2026