you have a reserve of a few gallons that's why the needle doesn't move very fast from the full b/c it is essentially over-full (at a higher level than the gauge can read)

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2006 BMW X5 4.8is Lemans Blue/Beige/Dark Maple
-Nav, Comfort Seats, Heated Steering Wheel,
Rear Airbags, AUX Input
2009 BMW M3 Space Grey/Black/Carbon
-all options