Every single gas price application uses the cash price. It's the standard unless credit prices are specified.
Again, please update prices using the cash price. All Wazers need to be using the same data entry process or this new gas price comparison functionality is totally useless since you cannot compare between stations effectively. It's bad enough that prices are already showing for grades of fuel that are not available (eg. Diesel).
If you pay with credit card you know you will be paying more in many cases. You surely already know which brands around you charge extra for credit.