Which Magazine recently published the results of their testing of 'super fuels' in cars and found that they made virtually no difference. In one case they measured a reduction in power using Tesco super unleaded. The oil companies are disputing the results but they would!
Some high performance engines are designed for use with 98 ron fuel but most are designed to run on standard 95 ron petrol. My own logic is that if the fuel mapping is set up for normal petrol then it is a waste of money using the super variety.
I do have concerns about using supermarket supplied fuels. My understanding is that most of them have a percentage of bio ethanol (alcohol) mixed with the petrol. Alcohol isn't as 'energy rich' as petrol so this could result in reduced power or less mileage than full 100% petrol. having said that I'm probably like most people in that I'll source my fuel wherever it's cheapest!
