Some states want debit cards, some want credit cards, sometimes you 'pre-authorise' at the pump, some pumps take PIN numbers, some pumps take ZIP codes, some pumps take Aussie 4 digit Postcodes with a '0' in front, some pumps take '90210', some states you can pump your own gas, some states you can't pump your own gas..... It can get complicated buying gas in the US.