Fuels for Spark-Ignition Engines — Typical Commercial Octane Ratings Select the most representative octane rating band for petrol (gasoline) commonly available at retail service stations.

Introduction / Context:
Octane rating quantifies a gasoline’s resistance to knock in spark-ignition engines. Choosing the right octane prevents pre-ignition and detonation, safeguarding performance and engine life. This question asks for the typical band encountered at retail pumps.

Given Data / Assumptions:

• Consumer petrol grades considered (regular to premium).
• Use of RON (Research Octane Number) or equivalent pump ratings, depending on region.
• Racing/specialty fuels are excluded.

Concept / Approach:
Common retail petrol grades fall broadly in the mid-80s to mid-90s octane range, depending on whether the posted number is RON, MON, or the average (R+M)/2. Regular unleaded is often around 87–91 (RON: ~91–95), and premium around 91–98 (RON: ~95–99). Thus, 85–95 captures typical commercial offerings worldwide.

Step-by-Step Solution:
Identify common consumer grades: regular and premium.Map regional posting standards to RON ranges.Conclude that 85–95 is the representative band for ordinary retail petrol.

Verification / Alternative check:
Compare typical pump labels in multiple markets: posted octane values cluster in the mid-80s to low-90s (or low-90s to high-90s RON).

Why Other Options Are Wrong:
95–100 and above correspond to premium/specialty or racing fuels not typical of all markets.110–125 are aviation or racing grades, not standard retail petrol.70–80 is too low for modern automotive petrol.

Common Pitfalls:
Confusing RON with MON or the anti-knock index; always note the rating method.

Final Answer:
85–95