i only get gas from husky or mohawk 91+ octane in both my 330ci and x5. I never go to shell nor esso no more, last time i put gas from shell into my x5, it screwed up my fuel level sensors, said it was empty, thought it was maybe just a slow sensor, sensor never went over the mid mark. I got gas again after from esso, did the samething, i was pretty sure it was the sensors that went bad. got gas from husky afterwards, my level finally came back to normal. Dunno, but i haven't got gas from shell or esso again.