I've always had pretty good luck with gasbuddy. Not sure how much of it is open source though. It is listed on github so access to source is available. Otherwise... https://alternativeto.net/software/gasbuddycom/
I've always had pretty good luck with gasbuddy. Not sure how much of it is open source though. It is listed on github so access to source is available. Otherwise... https://alternativeto.net/software/gasbuddycom/