2004 XJ8 GAS GAUGE

I just purchased a 2004 xj8 with 45000 mile on it.
The gas gauge stays at about 5/8 to 3/4 even after I toped it off.
any Ideas on what it might be. Will this be covered under the warranty.
 
Also because im new to Jaguar is there anything else I should be aware of or check on this year with this many miles before i bring it in for repair 
 
thanks in advance for your help.

I had a similar problem, the tank would read empty every now and then, and when it was actually empty of gas, would read a little over 1/4 tank. The dealer fixed it and had to run new electrical lines from the fuel pump. Your car most likely is out of warranty since the manufacture date is likely 2003 september

Smallish technical point but doesn''t warranty dating usually start at first ownership sales contract, rather than mfg. date?

This is true, Jag calls it the in-service date. My car was manufactured in May 04 but not put in service until mid Septemeber of 04 so it is still in warranty, but not for long. You can call the Jag central number to verify your warranty dates.

may need a instument pack or most likely needs 2 sending units.. over time the plastic warps or falls apart or gets corroded from water in the gas..

I''ve (04 XJ) also had a problem with the fuel guage. Once I filled up the tank, it would read empty after starting up. Then it stayed on empty (even tho it was just filled up) until the next start and then it would read Full. This went on a couple times more and it hasn''t happened again.
 
My warranty is nearly over, too. Maybe I should I have the dealer fix? Is this a common problem that they''ll recognize right away?

My experience with the warranty is that if it does not fail for the dealer, it will not be getting fixed under the warranty. Be sure he sees the failure, he will then have to fix it under the warranty terms.