Won't MPG data be skewed if not filling from 0 to 100% every time?

[kingmustard]

Surely Fuelly can only figure out the MPG if you fuel the car from 0% to 100% every time, as it's based on the amount of fuel going into the car times by the odometer reading?

The issue is, no car is at 0% every time you fill up.

If it's at 10% (which is probably when most people go to fill up), would the MPG data not will be skewed, therefore meaning it's probably preferable to just rely on a car's LCD MPG data?

Just a thought. I may be wrong.