If you can check your gaslog and/or remember milestones (like say hitting 105k on the odo recently, something similar) you could probably figure out how many miles you have on this tank. I keep maintenance logs on my car and whenever I do something I record the mileage so at any given time I can figure out mileage on a tank from the most recent record compared to the odo.
I disconnect my SG everytime I park my car, too risky leaving it connected and on display for someone to swipe... maybe that's where all my inaccuracy is coming from w/ the tank readings?
Nothing remarkable happened on this tank. If I remember it had roughly 150 to 170 miles on it when the odometer was reset, and it had 120 miles on it when I reset again when I actually filled. I went anywhere between 250 and 270 miles on 19.3 gallons of fuel. On a side note I hope the station I filled at had E Zero gasoline. I was so far out in the woods that they didn't even have vapor recovery on the pumps.