Awesome: I would patent this, you will put big oil and all of the Middle East out of business.
Crawl under the rear, locate the plug the goes into the fuel tank and disconnect it. Hopefully the gauge will now read 0. If it does you know the sending unit is bad and take appropriate action. If it doesn't change, then you have a wiring issue, a good place to start is to remove the gauge cluster and check the ribbon cable. It has a tendency to get corroded at the plug and sometimes the traces get burned. There are many posts on repairing, jumpering, and replacing the gauge cluster.
Let us know what you find, and get back to us.