Every time I full tank the car ( I fill it up all the way) the needle on the cluster and on the on board computer stops on 253 mi and slowly goes up as you start driving. The dealer suggested that it was the cluster. The car stayed at the shopps for a month. They said they did several tests to it and that it's fixed. The truth is I full tanked the car yesterday and the same thing happened. Can this be from the fuel sending unit. Is it a hard thing to fix?