Don't use tesco stuff... I was using the 95ron sainsbury stuff for a few month because of how cheap it was. Normally, I use V power or BP Ultimate, but decided to go with the cheap stuff for a bit, felt everything was ok, but then last month, my engine warning light came on. Audi roadside assistance came over and reported that the ECU detected a misfire. Said it is most likely down to the lower grade fuel from the supermarket. More importantly, he mentioned that he has witnessed several other a2 running on tesco fuel that has caused problems and that I should avoid that brand. So maybe you should try the more premium stuff.