Fuel tank and filling up

Just been out to fill up, and when the tank is full to the lip if I wait about 15 seconds the level goes down by about 5cm and I can get another 0.5 of a litre in. This can be acheived many many times. As I'm off to Zolder I thought I'd try to get as much as possible into it. WOW, the fuel gauge says I have 16.6 gals in my tank, I won't be relying on that too much.

Any one know why I can get all these extra halves in, where is it going? I have checked under the car, no leaks and when I got home, 5 miles, the level was just a bit down the filler tube.

[Alpineandy]

I don't know about the extra halves, but I do know you'd have saved a fortune filling an empty (ish) tank on the other side of the train...

No time for filling up............................................ Must dash !

The fuel guage level unit itself fills up with fuel via quite a small hole - presumably so that it doesn't give fluctuating readings when the fuel sloshes around during cornering, braking, acellerating etc.. The effect you are seeing is probably just the unit filling up. I seem to remember that when I took it out, I had to leave it for a while to drain and that was only with a couple of gallons in the tank so I assume it takes just as long to fill up again.