Glossary “octane number” Definition:
The number representing the average blend of iso-octane with an index of 100, and other hydrocarbons with an index of 0, usually between 87 and 92.

Glossary “octane rating” Definition:
Term used for octane number. Measurement of a gasoline’s ability to resist engine knock. The higher the octane rating, the less prone the gasoline is to cause engine knock (detonation).

Glossary “octane requirement” Definition:
Minimum octane rating of a fuel required to operate an engine without a spark knock.

Glossary “octane requirement increase (ORI)” Definition:
Increase in octane requirement that results from the build up of combustion chamber deposits.

Glossary “octane enhancer” Definition:
Common term designating components that are added to gasoline to increase octane and reduce engine knock. Examples are toluene, ethanol, ETBE, and MTBE.