Which statement best expresses the octane requirement?

• A. A maximum of 91 octane.
• B. Octane must be exactly 91.
• C. Octane must be above 95.
• D. A minimum of 91 octane.

Answer: (D)

The main idea is that octane requirement is about the minimum fuel quality needed for the engine to run properly. Saying you need a minimum of 91 octane communicates that any fuel with 91 octane or higher will prevent knocking and allow normal operation. Using a lower-octane fuel risks detonation or reduced performance, which is why the other phrasings don’t fit: a maximum would wrongly limit higher-quality fuels, an exact value imposes an unnecessary restriction, and stating you must be above 95 implies a stricter requirement than necessary. In practice, you should use fuel that meets or exceeds the specified minimum octane to keep the engine running reliably.