Most of these types of gages are very inaccurate. If it has an external sensor, it could be misplaced or loose. If it has an internal probe, it could have stuff built up on it. when it builds up on the probes it can cause the misreadings. Check the tank to see what type you have If external you can check for mounting. If internal, they make degunker you can buy at camping stores, just follow the directions.
Some times, people just fill the tank with liquid and a lot of ice and take it for a joy ride. Hope this helps you.
2005 Safari Cheetah 38PDQ - 2009 Ford Flex
Me (Gatogonow), The Boss (DW), Honey Bunny, Maggie May and Mollie Kay (The Gatos)!