ScanGauge: How does it calculate?
 

OK so I have an issue right now with my fuel sensor and it dances around quite frequently. For the most part I know how much I have but it's not as accurate as it should be.

Does this mean that my ScanGauge readings will be inaccurate? If so, I might as well do the fuel pump now.

I think Scangauge has access to only the fuel consumption rate from the OBDII data stream, because the tank size is programmed in by the user during the set up process for the SCII. IOW, the fuel gauge in the car won't affect the SCII operation.

The fuel tank size or factory sensor have nothing to do with how the Scangauge calculates MPG. It only uses that information to calculate Distance to Empty.

The Scangauge and other MPG computers calculate MPG by reading the vehicles speed sensor to calculate distance. They also calculate fuel consumption over a specific time by using the constant stoichiometric mixture 14:7:1 and then using the vehicles mass airflow sensor (MAF) or manifold absolute pressure sensor (MAP) to determine how much air is used. Using the ideal 14:7:1 air/fuel ratio, we already know how much fuel is added based on how much air the MAP/MAF reports. That gives fuel consumption. The distance traveled over a finite amount of time divided by the fuel used over a finite amount of time gives us instantaneous MPG.

Perfect answer. Thanks for your help guys :)