I used my Discover card at the pump to pay for $48 in gas, but my card was charged $100; why?

Every credit card transaction at the pump is initialized with a pre-authorization to the card company. Stewart’s sets that pre-authorization amount at $1. However, some card companies, such as Discover, require that we pre-authorize for the maximum amount of gasoline that can be pumped in a single transaction at the pump. In this case, we allow for up to $100 to be pumped in one transaction. Once Stewart’s is paid and the amount actually charged to the card holder’s account, that $100 pre-authorization hold is removed from the card holder’s account.