My gas gauge decided to go haywire this past weekend. I first noticed it when I started the car and the needle started to bounce around.

Now I know the gauge isn't really reflecting what's in the tank...

I think I recall this being a problem w/ the sensor (in the tank)....is this a big deal for Audi Service to fix??

To replace the sensor is not a big deal. They just need access to your trunk/hatch.

I am hoping this is going to fix the problem. I have not had mine replaced as of yet. I am waiting on a part to make my stereo removable which will allow them complete access to the area.

Mine also went crazy. But the other functions had not failed (mpg, etc) so they replaced the cluster. It didn't work the very first time I refilled the tank but after that, it has worked perfectly.

It may not be the sensor (quattros have 2?)

This is a well documented problem on Audis. There's even a service bulletin for it for A6's.

Occasionally there is a buildup on the sending unit that usually have the guage indicate more gas left than actually is the case. The VAG tool will not catch this problem.

A simple cure is to use high grade gas, to add octane booster to a couple of gas tanks, or ofcourse replace the sending unit.

I only run 93 or 94 in my TT and I still have this problem. The sending unit will be replaced very soon.

STP Gas Treatment and Outlaw Octane Boost. Put both of these products on your next fill up.

Why? It's been documented that the amount of sulfur can cause some problems on the contact points of the sending unit. But by having a gas additive/cleaner and increasing Octane it can help clean the contact points.

It worked for me, and I haven't had any problems. It helps to use those products on a periodic basis as well.