The gas gauge on my 2000 E150 has been acting up. It worked fine when on full until about half tank and then it shows empty. This went on for a few months and I decided to use a solution that has worked for years on C5 (1997-2004 Corvettes). I know, I had one.
I poured in 3 twelve oz bottles of Techron to the gas tank. It's been 3 weeks and the problem has seemed to go away. Only time will tell.

Has anyone else experienced the same with their gas gauge?

 

I have, in fact on the same year but the E250 chassis. Once my tank is just below 1/4 tank dash gauge will drop below the E mark. Even when filled up it takes a road bump to jar the sending unit loose and the gauge start reading correctly again.

I too thought adding Techron "fixed" the problem but it doesn't, or at least didn't in my case---the problem remains. I rarely let the tank even get to 1/4 so for the most part this annoying thing isn't a problem any longer.