Fuel Gauge Inacurrate??

[53helofe]

So I have had my 01 X5 fortwo weeks now and I took it for a road trip this weekend. I would have to say that she did great all in all and it was a great drive. When I was nearing the end of my first tank of fuel, indicating just over 1/4 I looked down while I was driving and watched the fuel gauge start to rise and go back to indicating 1/1 Ithought man this thing gets such great gas milage that it actually replenishes itelf with fuel Ok, we all know that isn't true. When I stopped to fill her up I turned the vehicle completely off and then turned her back on prior to filling up and the gauge read just under 1/4, which is what she should have read.

Has anyone experienced this fule gauge going up while driving thing before, is it a common issue? Interestingly enough when I checked my miles remaining after it went up on its own, the milage remaining increased correspondingly.