We used to have a Ford Ka that was very sensitive to supermarket fuel. Fill up at just about any supermarket (Asda, Tesco, Sainsburys etc) and it would ping and miss. Fill up at BP or Shell and it would be instantly cured. Don't really know why this would be but a quick Internet search suggests it is all down to additives (that are not added to supermarket fuel). All I can say is our old Ka could definitely tell the difference.