We decided to take your advice and use Shell V-Power in place of supermarket fuel. When we started the trial, a petrol station attendant enthusiastically told us he had made an overall saving of 8 per cent when using it. Having reeled off 1900 miles our overall saving works out conservatively at 8 per cent, even after allowing for loyalty discounts. And the car (a Skoda Octavia 1.8TSI DSG) runs more smoothly. Thanks very much!