fuel gauge problem

Sometimes when I start my car my gauge goes all the way up when I know I dont have a full tank, And when mt low fuel light comes on the gauge slowly goes to half tank. Dont know if its the gauge or something else. Need help, Thanks.

could be a few things. can start with checking the connections to the ic cluster. some people have had problems with inaccurate fuel readings and they're solution to this was to take the pump out and bend the connector down to the band that it runs across for a better contact or re-solder the connectors on the fuel level sensor gage on the pump or replace the sensor all together. sensor costs i think 50 at gmpd.