For modified car insurance customers, opting for super fuels at the petrol pumps may be irrelevant to the vehicles performance according to a new report.

The consumer guide, Which? Car carried out tests on three cars, to see whether super fuels, which are more expensive, were actually making the vehicles more economical.

One of the cars, involved was the Ford Focus, 1.6, which although showed a “marginal power increase", when it was filled with Shell V-Power, the cost of using the fuel would amount to £115 extra than the standard fuel, if it were used for 12,000km.

Which? Car also found that Tesco Super Unleaded decreased the performance of the Ford Focus, while the BP Ultimate diesel made the performance and economy of another car, the Renault Megane 1.5 “slightly worse”.

Richard Headland, Which? Car's editor said: “For many cars it's a waste of money paying over the odds for so-called super fuels. The standard fuels we tested were all up to the job, whether from a major fuel brand or a supermarket.”