ok so heres more of an "your're not the only one" answer...
my pop'* 97 Limited had this issue. the car had 50,000 miles..
We went to the dealer and they gave us a brand new cluster. Our gas gauge was never accurate, infact before GM replaced the whole unit, their service guys reversed the connection for the gas, and it was always on E. This was what they did to see if the connections just needed to be cleaned, however sometimes odometers cant be fixed and need replacement. Believe me i remember those days, not fun.
Does your speed needle sometimes not work correctly? How many miles are on the car? I would also check out the Fuel tank sending unit. Im no expert on that, but it makes logical sense.
FYI - my sister inherited the car and to this day the cars run perfect besides that issue.