I won't buy gas on stations that charge more for credit than cash. It's a choice one makes.
Sorry gotta say something here. Do you know why gas stations started doing this? Because it is what the MasterCard/Visa merchant agreement tells them to do. No business can charge more to use a MasterCard or Visa but instead needs to provide a cash discount. Nobody did it and just charged more regardless if you used a credit card or not. So we all pay more for stuff because of this crap. Gas stations offered the cash buyer what they were entitled to anyways. Blame the greedy, rip-off, arrogant credit card companies for this behavior. Then to top it off they turn around and provide higher educational schools and government agencies (DMV) the merchant agreement addendum that they can change extra for using a credit card, bunch of ******** that isn't fair to the small business. Every time a business charged me extra for using a credit card, I threw the merchant agreement in their face and they always changed their tune. Had a big purchase once and that business wouldn't do anything so I disputed it with the credit card company and won. I commend gas stations for doing the right thing and being upfront with their customers and following an agreement that they made when accepting to take credit cards when others clearly do not.
Straight from the merchant agreement:
5.11.2 Charges to Cardholders
A Merchant must not directly or indirectly require any Cardholder to pay a surcharge or any part of any Merchant discount or any contemporaneous finance charge in connection with a Transaction. A Merchant may provide a discount to its customers for cash payments. A Merchant is permitted to charge a fee (such as a bona fide commission, postage, expedited service or convenience fees, and the like) if the fee is imposed on all like transactions regardless of the form of payment used, or as the Corporation has expressly permitted in writing
http://www.mastercard.com/us/merchant/pdf/BM-Entire_Manual_public.pdf