and after reading years of posts like these and similar tales of condensation, I began to worry. The tank spends much of it's time empty because I can't afford to fill it . . . and we get wild temperature swings here in Virginny. So -- one time the truck came for a fill, I asked the driver about it. He dabbed some stuff on a dipstick, dropped it in, pulled it out, and said, "Nothing in there."
I admit an oil-furnace burner isn't a diesel injector . . . but I don't seem to have a water problem in the tank.