Thanks madasafish
If the car is on a slope - in any direction - the fuel cut off will be affected by that. If you are filling brim to brim and the list is the passenger side below the driver side ,then the fuel filler pipe will fill up before the tank - which will have air trapped in it... and thus contain less fuel. Ditto if the front of the is above the back...
What's puzzling me is it happens when I fill at the exact same pump which is on the level. Makes me wonder if there's something up with the EVAP system though I can't see anything.
