Interestingly mine shows 1/4 if I leave the car running when filling it up from empty (isn't that dangerous- but when I'm talking on 2 cell phones at once AND working the pump there's often just too much happeneing to cover everything...)

The cap must need to have the ignition turned off in order for it to reset, otherwise the gauge will creep up ever so slowly as you drive along with your newly filled tank afterwards...

I know it doesn't help- but as an observation it might have some value one day.

I find that the gauge is pretty accurate apart from that.

Nick