Incorrect mpg

[Ciderbarrel]

What people need to realize is that when you use a partial fill after a full tank, that amount isn't how much gas you used to go the distance on your odometer, it is how much gas you put in your tank. It will be less than the amount you used.

When you do two partials in a row, you will never know how much gas you did actually use and you have zero accuracy in determining how much gas was used to go the distance you are accounting for.