FWIW - On most "do it yourself" gas pumps at the airfields I have flown
into asks a series of questions with the first being "have you ground
your aircraft," Followed usually by N number then amount to be debited
to card. I usually enter an amount that is roughly $10 to $20 over
what I think I need (adjusting of course for price flucuations). Once
this is done the most I could lose would be $10 or $20 bucks. the pump
will automatically shut off at the higher limit.
What was the upper limit you expected to reach?