When you use any type of card, credit or debit, but you go in and tell the cashier a fixed amount in advance, there is no hold. With the risk of losing money at gas stations, the general rule of 2 Wants To Know to protect your money at gas stations is to dedicate a credit card to gas. This way, you'll quickly know if a scammer is using it to buy gas and if it's a credit card, so it's not linked to your bank account. Remember that just because a debit card works like a credit card doesn't mean that your money is as protected as a credit card.
A debit card, even if you use it as a credit card, is still linked to your bank account. This means that your money can be held or frozen, so you won't be able to use it until the transaction is effective. Notifications can be turned off at any time in the browser settings. The good news is that, ultimately, you won't have to pay for more gas than you actually take out of the gas station.
But the bad news is that the withholding imposed on your credit card for that larger amount could last several hours or even several days. And that could be problematic if you're getting close to your spending limit and your billing cycle hasn't ended. In the meantime, if you don't like the idea of a major hold being placed on your credit card to refill it, you can always ask a gas station employee to pre-authorize a smaller transaction (that is, to put a lower hold on your card). When you use a credit card to fuel your car, gas stations may hold your card for a certain amount.