If your credit card bank and swipe machine bank is not same, then the swipe machine bank is charged you 2.5% extra.
example: you have HDFC bank credit card, the petrol pump guy having CITI bank swipe machine. when you spend 230/- rupees on petrol, then you have charged 240/- rupee.
In case of same bank swipe machine and credit card, then there is no extra charge.
So before spending anything, verify the swipe machine. then use your card.