I'm actually not quite sure if it is the fuel gauge or something else but when I fill my tank all the way to full, the gauge still stays on empty for about 15 minutes and then slowly makes its way up to full. I have also noticed when I am driving that the gauge will drop back down to E and then go back up to F or sometimes just waver inbetween. Is this a problem with the gauge, oxygen sensor...or what?  

Sounds like you've got a sending unit problem. The Oxy Sensto has nothing to do with this.

Now, a Chevy gas guage will move as your driving as the fuel level drops, because of the gas moving back and forth in the tank. I have a '92 Silverado, my gauge does the same thing.

But, your slow movement from empty to full after filling up says that either the float arm on the sending unit is sticking, or the whole sending unit is going bad.

Here's a link to the LRS website where you can buy a new sending unit for a great price.

http://www.latemodelrestoration.com/iwwida.pvx?;item?item_no=GM-19121306%20%20%20%201&comp=LRS

A new sending unit form the dealership is gonna cost you and arm and a leg, trust me. They wanted almost $600 for the one for my truck!

I'd recommend you go ahead and change the sending unit. Whiel you're there, you should also change the fuel pump and screen. It's good preventive maitanence.  

hey, common problem with newer chevy and gmc trucks, will need to change fuel sender, the card on the sender gets dirty from the new fuel blends. after you replace sender try running fuel injector cleaner thru fuel tank every couple of months to keep problem from happening again. you could get sender from dealer, they call it a fuel level sensor. they may not offer it anymore, you may have to replace pump assy.  

buchanan842:  Where is the sender located?  

the sender is on the fuel pump in the fuel tank. if you have never replaced one before, you should have a shop do it for you.  

I am having the same problem with my truck.  I have been told that it is the fuel sensor in the gas tank and the dealrer wants $400 to fix it.  This seems to be a reoccuring problem.  I have heard of a lot of people having this problem.  you would think that GM would do something about it instead they make us pay for it so they dont have too.