Octane Rating Label Check
Compare manual and pump octane labels only after confirming their rating scales.
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Octane Rating Label Check
Compare manual and pump octane labels only after confirming their rating scales.
Data last maintained
About octane rating labels
RON, MON and AKI are different scales
RON is the Research Octane Number and MON is the Motor Octane Number. AKI is the Anti-Knock Index shown as (R+M)/2. A number has meaning only with its scale, so a lower-looking AKI value can describe fuel that also carries a higher RON value.
When an exact AKI calculation is possible
AKI can be calculated exactly only when both RON and MON belong to the same fuel: AKI = (RON + MON) / 2. RON alone does not determine a unique MON, so this tool never presents a fixed RON-to-AKI conversion as exact.
What the verdict does and does not mean
A passing result only says the pump value is not below the manual's stated minimum on a confirmed common scale. It does not recommend a brand, judge whether higher octane improves performance, or assess ethanol compatibility. Follow the owner's manual and the complete pump label.
FAQ
Common questions and answers about this topic.
What is the difference between RON, MON and AKI?
RON and MON are results from different octane test methods. AKI averages those two results and is written as (R+M)/2. Because the scales are different, compare numbers directly only when both labels use the same scale.
Is 95 RON the same as 91 AKI?
Not necessarily. That pairing is a common approximation for some fuels, but RON alone does not reveal MON, so it cannot prove an exact AKI. Use both RON and MON from the same fuel, or follow an explicit AKI label.
Why can this tool not convert RON to AKI from one number?
The formula is AKI = (RON + MON) / 2. Different fuels with the same RON can have different MON values, so a single RON does not determine one exact AKI.
What if the manual or pump shows only a number?
Check nearby wording for RON, MON, AKI or (R+M)/2 and select only what is actually printed. This tool does not infer the scale from the number or country because regional conventions are not evidence for a specific label.
Which source should decide what fuel my vehicle needs?
Follow the vehicle owner's manual and any fuel-door label supplied by the manufacturer. This tool only checks whether two printed octane values are comparable and whether the pump value is below the stated minimum.
Does using higher octane always improve performance?
This checker does not make that claim. It only tests the printed minimum relationship on a confirmed scale. Whether a vehicle benefits from higher octane depends on its engine and manufacturer guidance.
Data Sources
This tool's data is compiled from the authoritative sources below.
- U.S. FTC - Complying with the Fuel Rating Rule(opens in a new tab)
- EUR-Lex - Directive 98/70/EC relating to the quality of petrol and diesel fuels(opens in a new tab)
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