WordGarden.iooctane
B2Pronunciation
UK
- /ˈɒkteɪn/
US
- /ˈɑkteɪn/
Meanings
Noun
the fuel-performance rating of gasoline or a similar engine fuel
a hydrocarbon with eight carbon atoms, used in chemistry and fuel science
Beyond the definition
You probably notice this word every time you fill up your car. It's the number, like 87, 89, or 91, shown on the pump. That number is not an ingredient in the fuel. It is a rating that shows how well the gasoline resists "knocking" in an engine, which is when the fuel burns too early. Higher ratings help high-compression engines, often found in performance cars, run more smoothly. For many everyday cars, a lower rating is fine. The word is also used in a figurative way to describe something full of energy or excitement, like a high-octane action movie.
Octane refers to a scale used to measure the resistance of gasoline to auto-ignition, more commonly known as "engine knock." Engine knock happens when the fuel-air mixture ignites prematurely in the cylinder, causing a rattling sound and potentially damaging the engine over time.
Originally, this rating was determined by comparing a fuel sample to a mixture of two hydrocarbons: iso-octane and heptane. Pure iso-octane has a rating of 100 because it resists knocking exceptionally well, while heptane has a rating of zero. Therefore, "87-octane" gasoline performs similarly to a mixture containing 87% iso-octane and 13% heptane. While modern fuels use various additives to achieve these results, the name "octane" has stuck.
Beyond the gas station, the term has seeped into everyday language as a popular metaphor for energy, excitement, or intensity. You might describe a fast-paced movie as having "high-octane action," or a charismatic speaker as possessing a "high-octane personality." So, whether you're concerned about your car's performance or describing something thrilling, understanding octane means recognizing its connection to stability, power, and energetic force.
Examples
- 1
Fuel requirement
The owner's manual says to use 91-octane gasoline.
- 2
Fuel grades
Premium gas usually has a higher octane rating than regular gas.
- 3
Engine knocking
If the octane is too low, some engines can start to knock.
- 4
Racing engines
Mechanics sometimes add special fuel treatments to raise the octane for racing engines.
More examplesFewer examples
- 5
Action movie
The sequel is a high-octane action movie with almost no slow scenes.
- Phrasehigh-octane
very energetic, fast, or exciting
See also
Forms and spellings
2 forms open this card.
Main spelling
- octanenoun
Forms
- octanespluralnoun