Definition

Noun: A numerical value that represents the resistance of a gasoline fuel to knocking or pinging in an internal combustion engine. It is a standard measure of fuel performance and quality.

Usage

The octane number is a critical specification for gasoline. A higher octane number indicates a greater resistance to engine knock, which is an undesirable premature combustion of the fuel-air mixture. This allows engines with higher compression ratios to operate efficiently.

Examples

• Noun:
  • Premium gasoline typically has a higher octane number than regular unleaded fuel.
  • The engineer checked the fuel's octane number to ensure it was suitable for the high-performance engine.
  • A car's owner's manual will specify the minimum required octane number for optimal operation.

Advanced Usage

• Research Octane Number (RON) and Motor Octane Number (MON): These are two different test methods for measuring a fuel's anti-knock properties. The octane number displayed on fuel pumps in many regions is an average of these two, called the Anti-Knock Index (AKI) or (R+M)/2.
  • The fuel was tested, yielding a RON of 95 and a MON of 85, resulting in a pump octane number of 90.

Variants and Related Words

• Octane rating: A common synonym for octane number.
  • What is the octane rating of this fuel?
• Knock resistance: A descriptive term for the property measured by the octane number.
• Anti-Knock Index (AKI): The specific average of RON and MON used as the posted octane number in North America.

Synonyms

• Octane rating
• Fuel grade (in a contextual sense referring to the octane level)

Related Phrases and Terms

• "High-octane": An adjective often used metaphorically to describe something as intense, powerful, or energetic, derived from the technical meaning.
  • The debate was a high-octane clash of ideas.
• Engine knock / pinging: The undesirable condition that a sufficient octane number prevents.
• Compression ratio: An engine design factor that determines the required octane number of the fuel.

Noun

1. a measure of the antiknock properties of gasoline