Ethylene dibromide in aviation gasoline serves to scavange lead oxide from the cylinder combustion chambers. Which of the following is its function?

• A. To raise octane rating
• B. To reduce evaporation losses
• C. To prevent water condensation
• D. To scavenge lead oxide from the cylinder combustion chambers

Answer: (D)

Lead scavenging is the main idea here. In avgas that uses tetraethyl lead for anti-knock, lead oxide can deposit on the combustion chamber, valves, and plugs as the fuel burns. Ethylene dibromide is added to react with those lead oxide deposits, forming lead bromide, which is more easily carried away with the exhaust. This keeps the combustion chamber cleaner and helps prevent lead buildup on critical parts. So its function is to scavenge lead oxide from the cylinder combustion chambers. It doesn’t primarily raise octane, reduce evaporation losses, or prevent water condensation.