A business method prompts users of electronic payment cards and automatically adjusts automobile fuel pricing based upon the number of passengers in a vehicle at a refueling station. When the driver stops to refuel the vehicle, the system prompts the driver to insert a payment card to pay for the fuel. If there are other passengers in the vehicle, they too are prompted to insert their cards to indicate that they are riding with the driver. The system is provided with numerous protocols for ensuring that the system is not inappropriately circumvented. For example, the system can verify that the additional cards are not from other patrons at the same service center, or that the additional cards are not from other family members of the purchasing card holder. After all cards have been read and verified, the reduced price of the fuel is displayed and the fuel is dispensed.