gas tank size on duster??

I have seen other guys on here with the same problem. is always the same thing gauge reads empty and will take in about 10 more gallons and reads full. they put in new sending units and nothing happens better, I guess I can try either siphoning out whats in the tank when on E or keep a couple gallons in the trunk and keep driving on E till I run out, keeping track of how many miles I go before it dies out. this seems to be a common problem!