Superfuels: are they worth the money? - Super fuel: the promise

Our investigation shows that you could be shelling out more without reaping any substantial benefits.

BP claims its Ultimate petrol can help you achieve up to 28 miles more per tankful and that its diesel equivalent can yield as much as 22 miles more. The company also says you get more power from both.

Our results show that from a typical 15-gallon tank, you'd travel 1.5 miles farther on Ultimate, but you'd pay an extra £6.14.

Shell, meanwhile, says: 'Shell V-Power could lead to reduced emissions and fuel consumption for many cars when compared to regular fuels.'

Total says it will refund the difference in price between its standard and Excellium fuel if customers do not see an improvement in fuel economy.

With laboratory-based evidence to support the claims, it sounds convincing.

Indeed, in a whatcar.com survey on premium fuel usage, 42% of respondents said they use superfuels all the time.