Mine is a little off but not too drastic. It will go a couple lines higher or lower depending on the driving I'm doing. Stopping and accelerating it will always go down but when sitting at a light I can watch it slowly go back up a line or two. I'd consider that normal. If it;s really jumping around like from 1/4 to a half then replacing the sending unit would not be a bad idea, our impala's gauge would go from full to empty randomly which was the sending unit.