Optimun Gas Fill up station and report
It would be very usegul to have a road map calculator to the most optimum gas station depending on the fuel consumption of your car (that you can report manually after each travel), depending of the gas price in eah station and depending of the traffic to reach that destination.
If you want to fill up just a couple of gallon it is not optimum to go to the cheapest one, instead you want to go to the nearest one, but if you want to go to fill a full tank it is more optimum to go to the cheapest one regardless of the fuel you are going to consume reaching there.
Also, it would be useful to add an optimum fel stop in the route you are planning. Whih is the most optimum place to deviate from your current travel to go to a specific gas station
There is already an application that does something similar in chile called "bencina" and it calculates the most optimum gas station based on distance, fuel consumption and price