Or capitalism

Yeah.

If you were a local they'd see you pull up and turn on the pump. If you weren't you'd go inside and pay cash first, but it was inconvenient because it was harder to just fill the tank.

I'm still pissed off at being treated like a thief every time I go to gas up because they started a forever war in the middle east which inflated the price of gas. Then they never brought the cost back down with the price per barrel AND kept the paying before pumping policy.

I'm 60, so me, too. But, I haven't seen a pump or a station that allows pumping before paying in many, many years.

You hand over cash at the counter, and they turn on the pump. Or you pay at the pump--you need to put your card in before the pump will start.

Well these days credit cards have an authorization function where they can hold $50 or $100 and then when done can release the hold and charge you the proper amount.

And cash is rare enough that they don't mind inconveniencing those people anymore.

Pay the clerk. If you can't fit x litres/gallons/whatevers, you go back to the clerk and they give you the remaining balance back.

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.

How do you fill your tank without paying for more gas than you're going to use?

you don't pay for more than you use. I prepay $100 on my credit card, use $58 and I'm charged $58, the $100 was a security hold and is the most you can get.