The sale of petrol with E10 ethanol (up to 10% ethanol in petrol) has been permitted in the UK since 2021, however the sale of fuels with higher ethanol content, such as e85 or e100, is only permitted to a limited extent.
Ethanol E85 is a blend of gasoline (15%) and ethanol (85%) produced from vegetable source materials.
As more effort is put into maximising an engine to take advantage of the higher "octane rating" of E85, engines achieve greater power advantages.
E85 has a higher octane rating than regular petrol at 87 or premium petrol at 91-93. This allows it to be used in higher compression engines, which tend to produce more power per unit displacement than their petrol counterparts.
E85 ethanol is used in engines modified to accept higher concentrations of ethanol. FFVs are designed to run on any blend of petrol or ethanol up to 85%, while in countries where the climate is warmer, FFVs run on pure alcohol. The new flex-fuel vehicle models are adapted to run on e100 regardless of weather conditions.
In the UK, e85 is available for private use in bulk.