Why Do Gas Pumps Sometimes Stop at Exactly $100?

At many gas stations, customers notice that the pump automatically stops at exactly $75, $100, or another round number. This can happen even when the fuel tank is not completely full.

This behavior is related to how payment systems authorize card transactions before the final fuel amount is known.

The Short Answer

Gas pumps sometimes stop at a preset dollar amount because the payment system places a temporary spending limit during the authorization process.

How Gas Station Payments Work

When a card is inserted at a fuel pump, the gas station does not yet know the final purchase amount. Instead, the payment network places a temporary authorization request for a maximum amount.

This authorization ensures that the account has enough funds to cover the fuel purchase.

Why the Pump Stops at a Fixed Amount

Pre-Authorization Limits

Many fuel stations set a temporary authorization limit such as $75, $100, or $150. Once that limit is reached, the pump stops dispensing fuel.

Card Network Rules

Card networks require merchants to verify funds before allowing purchases where the final price is unknown.

Fraud Prevention

Limiting the maximum amount reduces the risk of large unauthorized charges.

What Happens After the Purchase

After the fueling process is finished, the station submits the final purchase amount to the bank. The temporary authorization is then replaced with the actual charge.

During this process, some banks may temporarily display the transaction while the final amount is being confirmed. In certain situations, the bank may place an authorization hold until the final amount is posted.

Once the final transaction is submitted, the system replaces the temporary authorization with the completed purchase.

The Bottom Line

Gas pumps stop at round numbers like $100 because payment networks require a temporary spending limit when the final purchase amount is unknown. After fueling is finished, the system updates the charge with the actual amount.