For emissions reasons, higher octane ratings are allowed in Europe, but gas and petrol are essentially the same product

 

the latin words for rock and oil being petra and oleum. The word petroleum, then, has been around for much longer than the first cars, indeed it can be traced in that form to 14th century France, and so shortening this to simply ‘petrol’ meant a modern name for an ancient product.

So why do Americans call this ancient rock-oil ‘gasoline’? Petroleum as a word was around in Europe back when the North American mainland was being filled with enthusiastic European settlers and so it’s likely those first English-speakers were aware of the term, but it’s only when this ‘rock oil’ was started to be split into different compounds did the term ‘gasoline’ come about. In a lot of organic chemistry, -ene or -ine is used (think benzene/benzine), and so the part of the petroleum distilled-off and used in motor vehicles was the part of highest volatility, and in time was dubbed gasoline.

Until recently it was thought the ‘gas’ part of it was due to it’s nature of being quite gas-like, however, it may have actually come from a brand name of Cazeline (a product sold and imported into the UK by a Mr John Cassell, and so named after him – Cassel + ine), which, when made by others who were not allowed to use the brand name, began being sold as Gazeline – or, in time, ‘gasoline’.

https://www.adrianflux.co.uk/uk-us-car-part-names/petrol-tank-vs-gas-tank/