Originally Posted by madpogue
Sometimes it's not just the gauge. It's been reported that the screen at the bottom of the pickup tube sometimes falls off, and thus the tube can't draw any fuel below about 1/4 tank. I don't know of any way to test/inspect for that, short of dropping the tank (or pulling the bed) and removing the pickup / sending unit gizmo.
Yeah, I guess I was overly specific there.
I was mainly commenting on the fact that the OP has his fuel guage read empty, but thinks there is still at least five gallons of diesel in the tank. Hell, it could be alot worse. I had an '87 F150 that would run out of fuel with the guage still reading half a tank!
Oh and by the way, my '97 F250 has an 18 gallon front and 17 gallon rear for 35 gallons total. So I'd say your fuel guage was pretty darn accurate if you're pumping 15 gallons in on "E".