Just to make you feel better (?) our petrol costs in the UK are enormous, largely because the government sees motor fuel as valuable source of revenue and it’s heavily taxed.
Our existing petrol standard is moving from ‘E5’ (97+ Octane unleaded with up to 5% renewable ethanol) to ‘E10’ (95 Octane unleaded with up to 10% renewable ethanol). The latter is unsuitable for some older vehicles, so forecourts offer both at present.
Currently you can expect to pay around £1.86 per litre ($8.38 per US gallon) at a supermarket filling station, around £2 per litre ($9 per US gallon) at motorway service stations and around £1.91 per litre ($8.60 per US gallon) on average.
Supermarket petrol doesn’t have the same improvement additives as ‘branded’ fuel and generally whatever you save on pump prices can be cancelled out by lower mileage per litre, although they often also offer discount vouchers for their petrol above a certain spend on your groceries. That will usually tip the balance in favour of unbranded supermarket fuel.
