Both of the banks who issued the credit/debit cards I use have protections in place which kick in when you travel. A couple of hefty fill-ups on the same day at service stations outside your home area can look like fraud. I once had a card refused for this reason and learned about how to avoid this. You simply tell the bank when you'll be traveling, and where. There's a place on the bank web site to do this, or you can call them if you like listening to canned music while on hold.
Simple. I have to confess my initial reaction was annoyance, but it's a small price to pay for not having to untangle the complications of credit card fraud. Thanks, banks!
I can't believe I just thanked a bank.