Common knowledge is entirely faulty.

Fuel oil when manufactured (cracked, etc.) is rendered essentially
'dry'. Water (vapor in the air) 'equilibrates' eventually until the
oil is saturated with water from the atmosphere ..... and only after
the oil is SATURATED with water does the 'condensation' become
apparent. Simple speak: if your fuel is condensing water it means
that its laid around with an open vent too long and its now LOADED
with water.

The BEST is to totally empty the tank for the winter, take home the
fuel and burn it in your heater.
EMPTY tanks dont magically fill up with water because of a mysterious
'condensation process'. :-)