I wonder how they would know how to contact you if the fuel was contaminated like last time.
You could use any old credit card to buy or, or someone elses for that matter.
If using my credit card in the long term equals a lesser price for AVGAS then that's a good thing. It must have been costing them too much to be giving everyone 30 days credit - can't blame them.
If the CC system works well, then so be it.