MPG Not Registered on Each Fill Up
 

On the log book it shows my fill ups, but the MPG on every other one is zero. I don't do anything different to enter data. Any reason why?

first of all, you should probably delete the first entry. You start with a full tank, log your mileage and fuel purchases after. One tank is marked as a partial. When a tank is marked as partial, no MPG calculation is made for that tank or the next one. This data is used in your overall fuel economy average though.