I wasn't suggesting that it's a deal. It's a penalty for the credit purchaser as the gas station is pushing the transaction fees for use of credit onto the consumer. The retailer pays a fixed fee every time a card is swiped. I believe they also pay a variable fee depending on the size of the transaction.
We don't do gas, but our CC account charges us a per-swipe fee, a flat fee +% of trans for debit, a different flat fee and % for credit, a batch fee to run the cards at the end of the day, and a monthly fee. If you don't close your "batch" out within 24 hours, the % per trans goes up.
For someone spending $50 on 15 gallons of gas, a surcharge of $0.10/gallon is enough to cover the cost of running the card if you have more than 20 CC transactions per day. Our cost to run a transaction that size is about 2% for debit, and 3% for credit on a typical day.
We've thought about adding a surcharge to credit card payment, or doing a minimum credit card amount, but so far we feel the cost (hassle, explaining/arguing to/with customers) don't outweigh the 2-3% gain from implementing that policy.
If your retailer isn't checking your ID everytime they run your card (we do), they're getting hit with chargebacks from stolen cards that drive up the price you pay. We've never run a stolen card, and that keeps our costs a lot lower, since chargebacks and associated fees are typically for 2-3x the amount stolen, and the retailer has to eat the cost.