In Canada its an auto function of the payment system. You say you want $100 in gas. The card gets preauthorized for $100 to ensure the money is available then the pump starts. After you finish pumping and get only $80 in fuel that is what is actually charged to the card. The card is charged only after you finish pumping.
Then you pay at the counter for the amount of gas you want to pump and if you overpay you go back to the counter and they give you back the difference.
In most of northwest europe this is standard. Otherwise how do you know how much you need pay to fill the tank?
That is definitely not true. There is no gas station here where you can do that anymore without having either signed in via an app or credit card.
It used to be like that, but that was a long time ago.
In Canada its an auto function of the payment system. You say you want $100 in gas. The card gets preauthorized for $100 to ensure the money is available then the pump starts. After you finish pumping and get only $80 in fuel that is what is actually charged to the card. The card is charged only after you finish pumping.
What if one only as cash?
Then you pay at the counter for the amount of gas you want to pump and if you overpay you go back to the counter and they give you back the difference.