Possible VZ SV6 fuel problems?

[1FATVZ]

Hey guys,

I'm not sure if these issues are normal or if theres a problem somewhere,

On average, my fuel consumption is around 14.3L/100Km with minimal highway driving and the majority being normal moderate city driving, i fill up every Thursday and never fail to hit the 'low fuel' warning.

I reset the trip every week and on average id say im getting about 430-450kms.

PROBLEM 1:
ive noticed is that when filling up, im putting in about 65 Litres of fuel meaning there is still around 10 Litres left in the tank, is it normal for the gauge to be telling me that theres ~25km till empty? in theory shouldn't this be closer to around 80 or so?
but i guess the 'till empty' isn't very accurate or something, just not sure how other peoples are...

PROBLEM 2:
Now, is my 05' Auto sv6 using too much fuel? my brother has an Auto 04' SV6 and he is getting around 600kms per tank compared to my 430-450, i also believe that their may be a problem with my fuel gauge or something similar. The problem that i have noticed has been how fast the bottom half of my fuel decreases. The top half may get me around 270kms and before i know im in the red zone around 160kms later, is this normal? or is there something that needs to be looked at?

Sorry for going on and on, hope you guys can help me out.
cheers

[impulsive]

Fuel Readings are like mens doodles, mostly over exaggerated.. i get no more the 550L per tank usually 500L. i have the same issue, the top half lasts for 400, then boom low fuel..