My experience with Fuelly shows very inaccurate MPG. My confirmation comes from Fuelio and zebra who both agree on stats. So Fuelly what happened ? Is it because your working on US gallons maybe ?
To piggy-back off of Draigflag I show your profile settings set to Metric units (liters, km, l/100km) but your vehicle profile is set to track in Liters and Miles.
This could be where you're discrepancy is.
*Edit- Also, since your post wasn't related to the Partial-fill up discussion in the thread you posted in, I went ahead and moved your posts.