Drivers who fill their cars with expensive "superfuels" and expect to see big economy gains should think again, according to a report by What Car? magazine.

Real-world tests were carried out for What Car? by the AA’s former senior research engineer, Peter de Nayer. In these tests, high-octane premium fuels including BP Ultimate, Shell V-Power, Esso Supreme and Total Excellium performed little or no better than their cheaper equivalents, in spite of costing around 7% more per litre.

“Our tests show that premium fuels are an unnecessary expense with no major fuel economy benefit”, said What Car? editor Steve Fowler.

“The verdict is still out on whether superfuels prolong engine life, as fuel manufacturers claim. Nonetheless, even using the fuel companies’ own figures, you’re unlikely to travel 7% further on a tank of fuel for a 7% increase in your fuel bill.”

The top-performing fuel in What Car?’s tests was Sainsbury’s 97-octane fuel, which delivered 0.5mpg more than its 95-octane fuel ­ in real terms that means just 6 miles more per tank.

“Unless the prices of these superfuels come down, there are far easier and cheaper ways of reducing your fuel consumption and your car’s emissions”, added Fowler. “By changing your driving style, anticipating the road ahead and sticking to the speed limit, you can make fuel savings for free.”