Sorry but thats entirely WRONG.....

Fuel picks up or absorbs water because its DRY when its made; the heat
of distallation/cracking drives all the water out of the hydrocarbon
mix.
IN a tank thats vented to atmosphere, chemical equilibrium will drive
water vapor INTO the fuel through the vent until the fuel is fully
saturated with water. The tank does not 'breathe', the oil does not
'breathe', etc. Water vapor keeps on absorbing INTO the fuel until
its saturated to an equilibirum condition of saturation.
If you have water condensation on the walls of the tank it means that
the oil is already fully or nearly saturated with water vapor. Has
NOTHING to do if the tand is full, 1/2 full, etc. Empty tanks do not
gain water .... ask yourself why?

The ONLY way to keep water out of a fuel tank that is vented to
atmosphere is put a water adsorbing desiccant breather filter on the
vent line .... or if the the tank is rated for full vacuum (no boat
or aircraft tanks ever are) simply CLOSE the VENT line VALVE when not
operating.

:-)

In article , Larry
wrote:

"Roger Long" wrote in
:

'm thinking that filter changes, in the absence of picking up some
problem fuel, should be a function of the total amount of fuel that
flows through the filter and not an automatic once a year thing.

You've failed to mention the MOST important function in good fuel
management.....refilling the tanks.

Didja ever notice what all the light plane pilots do, religiously, when
they return to the airport, but before putting the plane in the hangar?
They visit the fuel dock and REFUEL....even if it only takes 3 gallons.
Why??

A fuel tank not full to the filler neck "breathes". At night, when it
cools, it breathes in that water-soaked evening air that wets everything
with dew...including the inside walls of a half-empty fuel tank. As the
condensation continues in the night, the water forms into droplets too
heavy to stick to the tank and slide down the walls. As the water is
heavier than the fuel, gas or diesel, it slides down UNDER the fuel,
making a layer of water that increases every daily cycle....well, until
either the black algae that grows in the dark in the layer between the
fuel (food) and the water (water)...gets sucked up to clog the fuel
filters or injection system.

When the sun rises, the half-empty fuel tank on every sailboat in your
marina pressurizes and blows out the air inside it so that it can suck in
that next load of wet night air, tomorrow night. Gas powered boats do
even better! They blow out the light aromatic elements in gasoline that
give gas its octane rating....eventually turning the light gas into heavy
shellac...that brown lookin' "bad gas" everyone tells you about.

And all you have to do to stop it dead in its tracks is to take the time
to stop at the damned fuel dock and top off the tanks before heading to
your slip......even if it only takes a gallon. Full fuel tanks NEVER
have "water in them".....in the hangar at the airport.

Larry