Digital fuel gauge accuracy?

[MrSam]

I did a quick search on the accuracy on the digital fuel gauge (displayed on the screen in the center of the gauge cluster). All I got was that once it hits zero, you still have about a gallon or two in the tank.
What I'm wondering is, how accurate is the gauge, in general? I parked my car 2 days ago, just as it dropped from 330 miles to 325. Drove it to work today, and less than 2 miles in, it dropped down to 320. Total distance from work and back was 7-8 miles, but according to the digital gauge, I drove 30 miles (dropped from 330 to 300, after 8 miles of driving). I wasn't running AC, nor was I driving in sport. Just a casual drive to and from work.
Is this common? I'm coming from an Altima, and never had this "issue" with the digital gauge.
Car's a '11 A4 Quattro. Only upgrade is a K&N Intake. Brand new P Zero tires.

[adamazing]

I basically stopped paying any attention to it years ago. That's how accurate it is.

It bases it's estimate on your past consumption, driving style, meshed with current fuel levels and throttle position. It's always trying to hit a moving target.

[MrSam]

I basically stopped paying any attention to it years ago. That's how accurate it is.

It bases it's estimate on your past consumption, driving style, meshed with current fuel levels and throttle position. It's always trying to hit a moving target.

Ah, so it's not solely measuring what's in the tank, rather it's using some kind of inaccurate algorithm? I'll stick to the analog gauge, that doesn't seem to drop as fast as the digital one.

[jfo]

The normal fuel gauge uses the fuel sender unit attached to the in-tank fuel pump. It has an old fashioned, generally reliable float mechanism. The miles-to-go in the display is just a forecast as adamazing said. Helpful if you're on a highway trip and need an idea of distance to go, based on recent driving habits.

[Lambda13]

The normal fuel gauge uses the fuel sender unit attached to the in-tank fuel pump. It has an old fashioned, generally reliable float mechanism. The miles-to-go in the display is just a forecast as adamazing said. Helpful if you're on a highway trip and need an idea of distance to go, based on recent driving habits.

On my Yukon it used to go to 0 and then low... Fun times.

[twixinthemix]

Mine will say 405 miles at full and I have never gotten more than 250 miles from 3/4 of a tank.

[MrSam]

Thanks, everyone. That explains why the estimation is always bouncing around. Last night I drove a total of 50 miles. According to the digital "gauge" I gained 5 "miles to go"