FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationEasy
What is the primary purpose of tetraethyl lead (TEL) added to aviation gasoline?
- ATo lubricate upper cylinder components
- BTo act as a fuel system icing inhibitor
- CTo increase the antiknock (octane) rating and resist detonation
- DTo color-code the fuel for grade identification
Show answer & explanationAnswer & explanation
Correct answer: C. To increase the antiknock (octane) rating and resist detonation
TEL is an antiknock additive that raises the effective octane/performance rating of aviation gasoline, allowing higher compression and manifold pressures without detonation. Fuel color comes from separate dyes, and TEL is not an icing inhibitor or primary lubricant.
Why the other options are wrong
- A. Upper cylinder lubrication is a secondary/minor effect, not the primary purpose.
- B. Icing inhibition is provided by additives like FSII (EGME), not TEL.
- D. Fuel color coding comes from dye additives unrelated to TEL.
Tetraethyl Lead (TEL)
An antiknock compound added to aviation gasoline to increase its octane rating and resistance to detonation.
- Raises effective octane/performance number
- Allows higher compression ratios and manifold pressures safely
- Excess lead deposits can foul spark plugs, requiring lead scavengers like ethylene dibromide
Memory trick: Lead in the tank keeps knock in check.