Fuel RON conversion?

[Steve_M]

UK pump Super unleaded is RON 97-99 dependent on supplier.
US pump Super unleaded is RON 93

Does anyone know the conversion math between UK RON & US RON values?

[GavinPearson]

The US fuel is measured as an average of RON & MON.

UK fuel is say 98 RON or 95 RON.

US fuel is say 87 (R+M)/2 for Regular all the way up to 91 to 93 or 94 for Premium.

I would say that US premium is around 97 or 98 RON.

[Steve_M]

Thanks Gavin.

Found this too which explains it more.

RON & MON

[M3 Mitch]

Actually you can't convert RON to MON/RON average. *Typically* RON is about 3 to 5 points above the average, but since you don't know what the spread is, you don't have enough information to make a conversion.

My impression is that European fuels are somewhat higher in octane than US fuels of the same designation, but don't have any data to back that up either.