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AVGAS contamination of jet fuel

Aviation Mechanic General (AMG) practice question 19 of 26 on Ground Operations and Servicing. ACS element AM.I.F.R4 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAdding AVGAS to the jet fuel of a turbine engine can cause

  1. Adetonation and an immediate loss of power.
  2. Bmicrobial growth in the fuel tanks.
  3. Clead deposits and reduced service life.
Show the answer and explanation

Correct answer: C. lead deposits and reduced service life.

  • A — incorrect Decreased power and detonation damage are the effects of adding jet fuel to AVGAS in a reciprocating engine, not of AVGAS in a turbine engine.
  • B — incorrect Microbial growth results from free water in jet fuel, not from mixing in AVGAS.
  • C — correct The handbook states that adding AVGAS to jet fuel can cause lead deposits in the turbine engine and lead to reduced service life.

BACKGROUND

Misfueling is a serious hazard, and the fueling checklist directs the person fueling to ensure the proper type and grade of fuel is used and not to mix AVGAS and JET fuel. Adding jet fuel to AVGAS decreases the power developed by a reciprocating engine and can damage the engine through detonation, with possible loss of life. Adding AVGAS to jet fuel can cause lead deposits in the turbine engine and lead to reduced service life. Before any mixing is contemplated, the Type Certificate Data Sheet for the powerplant must be consulted.

STUDY TIP

Keep the two misfueling effects straight: jet fuel in AVGAS means detonation and power loss; AVGAS in jet fuel means lead deposits.

KEY POINTS

  • AVGAS in jet fuel causes lead deposits in the turbine engine.
  • Jet fuel in AVGAS causes power loss and detonation damage.
  • Do not mix AVGAS and JET fuel.

SOURCES

  • FAA-H-8083-30B ch01 "Types of Fuel and Identification"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.