We travel in the US all the time, and I have read and tried all the tricks, but I simply go to a ATM and take cash out so I have a few days gas money on hand. Our bank has a partner bank in the US that has no fee US withdraw (Scotiabank & Bank of America). That way I do not have to carry large amounts of cash and it is so much easier. I have learned to be good at estimating how much it will take to fill my tank and I will always put down a little extra just to be sure and sometimes I have to go back in and get a few bucks back, but most times, I get a full tank. I will use my card for most everything else, but for gas it is simply not worth the hassle. It is also handy to have cash on hand for tolls, coffee etc.