Ambitiously-named "super fuels" fail to help motorists' finances or improve green issues, a British consumer group has claimed.
Which? Car magazine said these fuels do not save drivers money, enhance a car's performance or do anything to aid the environment.
The magazine's editor, Richard Headland, said many drivers would be "wasting their money" by paying over the odds for these types of fuel.
Which? Car tested Shell V-Power, Tesco Super Unleaded and BP Ultimate Diesel against standard fuels.
It found Shell V-Power gave a Ford Focus 1.6 a marginal power increase. However, filling the car on this petrol for 12,000 miles will cost £115 more than using Shell's standard petrol. Tesco Super Unleaded was found to actually decrease the power of the Focus.
The Volkswagen Golf's hi-tech 1.4 TSI engine responded well to Shell V-Power, but there was little to choose between super fuels and ordinary petrol on economy and emissions.
The economy and performance of the Renault Megane 1.5 diesel were both slightly worse using BP Ultimate diesel, the super fuel furthest from the marketing claims in the test.
And each super fuel had only a marginal effect on the emissions of measured pollutants, seemingly putting paid to environmental claims, the magazine concluded.
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