I have a big green outside oil tank.

There is a tube on the outside, with a small floating ball in which is
supposed to show the amount of oil left in the tank. Near the bottom
(but not right at the bottom) of the small tube is a button you pull to
sync the tube with the tank.

At the very end of the tube, past the sync button, looks like a small
plastic container with a kind of empty/full indicator gauge on it, with
various markings on it to indicate how much oil is left in that little
container. (perhaps)

My question - can I allow the oil to fall right the way down the tube
and actually go past the sync button, and hope that it keeps falling so
that eventually the plastic container at the very bottom of the tube
runs dry - and is it at that point that I need to fill up the tank?
(Strapped for cash atm, and want to avoid getting oil as late as poss.)

Thanks, regards, dnw.