Not sure, but I was talking with my Dad this weekend about our computers and what not.. Although they need to "relearn" at times, they are sensitive to the driver itself. For instance, when I accelerate even if not WOT it will accelerate almost like WOT per my driving habits its learned. Its possible it reads a better spark and cause of his driving habits its dumping more fuel in to accommodate the better spark, but Im trying to figure out why mine as dropped with no change to the XK at all. Im guessing just how heavy my foot is but Ive been nursing her around and my mpg is going down! Maybe a good question is what fuel type are people using and which gas station?? I wish there was a race trac around here I always got waaay better mpg with their fuel..