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What Does Octane Rating Mean?

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Definition:

Octane rating is a fuel's ability to resist detonation and is classified by three main rating types:

All tests use blends of iso-octane and heptane as the reference fuels.

RON (Research Octane Number) is determined by burning fuel in a test engine running under mild and low load conditions, and comparing the results to the reference fuels.

MON (Motor Octane Number) is determined by burning fuel in a test engine running under severe and sustained high load, high speed conditions, and comparing the results to the reference fuels.

(R+M)/2 (Pump Octane Number) as the name implies, is determined by adding together a fuel's RON and MON ratings and dividing by two. This is the common rating found on pumps in North America.

Pronunciation: ok tayn ray ting
Also Known As: Octane Number
Examples:
Ethanol has an (R+M)/2 octane rating of 113.

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