Question of the week: Why is 100 RON petrol not sold in the UK?

David Ross, Editor
Sun, 15 Jun 2025

Dear Honest John,

"Recently while on holiday in Greece I noticed that some petrol stations were selling three grades of unleaded petrol - 95, 98 and 100 RON. The first two are readily available in the UK, but I cannot recall seeing 100 RON for sale in this country. Why is it not sold here and would it give a petrol or petrol/hybrid car an advantage?"

- JRP

Dear JRP,

Most fuel stations in the UK will sell two grades of unleaded - standard 95 RON and super unleaded which is usually between 97 and 99 RON, including Shell V-Power, Total Excellium Unleaded and Tesco Momentum 99 which are 99 RON.

BP did sell 102 RON fuel for a limited time at a small number of filling stations, but this has been discontinued. It possible to purchase petrol that is rated 100 RON or even 115 RON in the UK, but this is typically sold as race fuel by mail order, and at £7 a litre + VAT it would make little sense for a typical driver.

Generally speaking high octane fuels only bring tangible benefits for performance cars, as the ECU will adjust the engine's parameters to get the most benefit from the higher octane, with the potential for a marginal gain in power output.

While conventional petrol cars and hybrids may benefit slightly from higher octane fuel, as they have less performance to start with any improvement in power output will be even harder to detect. There may also be an improvement in efficiency, but even if it were to achieve a significant 5% improvement in economy, this would be offset by the increased price which could be 15% higher or more.

The reason 100 RON fuel it is not sold in the UK is likely to be a lack of demand, as BP's experiment with 102 RON fuel would suggest. Even with a filling station near Silverstone race circuit selling BP Ultimate 102 it failed to prove popular - and with a starting price of £2.42 a litre it's not hard to see why.

Ask HJ

Do I need to use high octane fuel in my Porsche?

Can you advise, my Porsche has 98 octane fuel printed on the filler cap. This is not always available and I use 95 Octane without any discernible effect, then filling the tank with 99 octane now and again to give the engine a treat, as it were. Is this as ridiculous as it sounds?

As you own a performance vehicle, you will benefit from maximum performance when using high octane fuel. Because it is a relatively modern vehicle, if it detects lower octane fuel being used it will alter the engine timing to avoid pre-detonation, but as a result you will not be achieving best performance, although you may have not noticed any difference. If you occasionally use higher octane but mostly use lower octane this may not be sufficient for the engine to achieve full performance. If it is affordable, we would recommend using higher octane whenever possible as it will ensure best performance and likely contribute to engine longevity and condition too.

Answered by David Ross

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