My gas mileage often floats between 30.0 and 30.5, depending on the amount of traffic I hit in a given week. I would like a better way to view my gas mileage so I can see when I'm close to increasing/decreasing by .01. Is there any way to quantify the amount of gas in my tank? I can assume the total number of gallons based on the size of the tank, and where my fuel gage is sitting; but this is only an approximation. Would I be able to get more of this info using an OBD2 reader (if so, does anyone have any recommendations for one that works well with Android)? How do you track your gas mileage?