Oh, also I forgot to add we always use Shell 91 or 93, whichever is available. In fact the X5 was in the shop for a transfer case issue a couple of months ago, and I told the SA to only fill up with Shell gas or leave it empty and I'll fill up when I pick up the car.
Now we use the cheapest gas available. Since the switch there has been no change in average MPG or performance.
