Mine actually is about the same maybe went up a couple (based on the dash indicator).
If you are going by dash number do you reset it after you fill up? If not try that and see what it says after reseting it. I have another car I have to reset it or the numbers get jacked up on the dash and read a lower avg. mpg. and I noticed a couple times on this when I would drive after fill up it would show lower than if I reset it after fill up.