Damn it where's 7th gear when you need it?!
The guages are electrical so you'll have either a problem with the sender unit in the fuel tank or the actual guage itself. Hope for your sake its the sender in the fuel tank because if its the guage its mega bucks to get someone to take your dash apart to get at it!! Get it tested for fault codes as it should show up where your problem is.
A4 3.0 Quattro Sport - Gone & missed everyday!
Current road going missile.....
........Smart Roadster - arguably the most fun you can have in a car without using lube!!