I cover a few miles at the weekends on the motorway. I know my 635 quite well. I know that if I was to put super unleaded in it so that it is more than 50% of what's already in the tank, it'll run like a bag of shit, occasionally cut out (which is rarest), the autobox has moments when it's not sure what to do, even on a run and its slightly lumpy taking off and under load. Run on regular and there is no faults like those mentioned. UNTIL TODAY! I covered 133 miles, fault free. I add £15 for the return journey and 2 miles down the road it all kicks off. I completed the return journey like this waiting for something to explode. It didn't. I've checked my receipt and correct grade was purchased. . The 635 had Tesco fuel from up here in Cambs, all OK, the return fuel was Tesco from north east London, all NOT OK. I do know this garage well and also know however that this garage has been closed for some time recently for major work but the garage looks exactly the same, even the courtyard.
So my question is this, has anyone else experienced fuel related issues recently and what work could have been carried out and could it of affected the fuel?