02-23-2021, 08:15 PM
In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index). Thus, 97 octane “super unleaded” in Britain is roughly equivalent to 91 octane premium in the United States. Most petrol in the UK and Ireland only has 5% Ethanol but that is likely to go up to 10% in 2021/22. My poor old 1952 MG won't like the extra Ethanol but I did change the fuel lines from the pump to the carbs with modern rubber to mitigate that.