Fuel additives and antiknock quality: Tetraethyl lead (TEL) was historically added to petrol (gasoline) to raise its octane number. Identify the best reason with respect to TEL’s intrinsic antiknock strength and blending effectiveness under standard SI engine octane tests.

Introduction / Context:
Octane number indicates a gasoline’s resistance to knock in spark-ignition engines. Tetraethyl lead (TEL) was widely used in legacy fuels as a powerful antiknock additive. This question checks conceptual recall of why TEL was so effective in raising octane ratings.

Given Data / Assumptions:

• Context is historical/technical (pre-unleaded regulations).
• Octane number scale is based on iso-octane (100) and n-heptane (0) reference fuels.
• We focus on TEL’s antiknock potency as a blending component.

Concept / Approach:
TEL provides free-radical scavenging in the end-gas region, suppressing pre-ignition/autoignition kinetics. It exhibits an extraordinarily high blending octane value (commonly treated as greater than 100 on the RON scale), meaning very small dosages markedly increase the pool octane of gasoline.

Step-by-Step Solution:

Verification / Alternative check:
Historical refinery practice and engine test data show significant octane uplift with a few milliliters of TEL per gallon, consistent with an effective octane value above 100 as a blender.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing the base fuel’s octane with the additive’s blending octane; the question targets the latter.

Final Answer:
more than 100