How can their be no fix to this? It must be something simple. My brothers VZ Calais has just recently started showing an erratic fuel gauge. It's got 135,xxxkms on it and has been fitted with a new fuel pump and fuel filter.
I figure temporarily, you can calculate the fuel used by the cars average fuel consumption (i'm not going to trust what it says now, but from past experience when it has been working properly, I have never seen it average more than 10.5L/100km. So to be safe, I'll say the magic number is 11L/100km.
The tank size is approximately 73L. Now by using your trip meter (which you will need to resest everytime you fill up a tank of petrol), you will be able to cover 663kms at absolute maximum before the tank is empty. Thus, once you hit 600 odd kms, go fill up.
For those interested, the calculations go like this:
11L/100km = 0.11.
73L/0.11 = 663kms.