My cars manual states that the fuel tank holds 17.4 US gallons. I am not one to be silly enough to let my car run out of gas but recently I had let it get down to the very bottom and upon fueling up was surprised when it took 18.66 US gallons. This is how much was filled with the pump automatically shutting off(no topping off). I was very surprised as none of my other Saabs ever did this. My curiousity made me try it again and once again I was able to fill it up 18.64 US gallons(no topping off). What I am getting at is if the computer uses overall capacity in its equation could this discrepancy be the reason for all the eratic MPG readings? Sorry for the long story. I am going to post this on a fresh thread for extra feedback.