Automotive
RON vs MON vs AKI
Quick Answer
This guide explains the three octane measurements and why pumps in different regions display different numbers.
By Everyday Solutions Exchange Editorial · Published Sep 2026 · Updated Sep 2026Reviewed by Everyday Solutions Exchange Editorial
This guide explains the three octane measurements and why pumps in different regions display different numbers.
RON
Research Octane Number is measured under one standardized test condition. Many countries display RON at the pump.
MON
Motor Octane Number uses a different test condition. For the same gasoline, MON is usually lower than RON.
AKI
Anti-Knock Index is the average of RON and MON. U.S. gasoline pumps commonly display AKI as (R+M)/2. A 95 RON label is not the same as 95 AKI.
What to check before you choose a product
Read the product label, confirm compatibility, follow the treatment ratio, and check the vehicle or equipment manufacturer's requirements. A related technical term should not be treated as proof of a finished product's exact composition.
Sources & References
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