jps wrote:
Doug, if the first filter is responsible for both large and small
particles, isn't it going to clog more quickly?


Nope. If the amount of gunk in the fuel is the same, then
the filter(s) will pick it up in pretty much the same time,
given the same fuel flow rate (within the limits of random
distribution).



The point is that you're distributing the gunk across a larger surface
area by doing it in series.


Which accomplishes what? I've heard it said that there will
be less pressure drop, which I don't think is true. Two
partially clogged filters equals two lesser pressure drops,
but if the flow is equal and the restriction is equal, then
is the pressure drop... what, not equal? And if the filters
are sized for the flow your engine needs, then the pressure
drop will not be large enough to cause a problem.



For example I use a Racor 45gph filter (which is very much
more flow than my engine will ever use) with 2 micron
elements in in, as a primary. It will seperate water and
trap everything I want to keep out of the engine. Changing
the element is much easier than rebuildin the injector pump.
It is rated at 45gph whether you put in the 30, 20, 10, or 2
micron element.

Obviously the 2 micron element will clog quicker, but that's
what you *want* it to do: keep that gunk out of the engine.
And why put in a 30 then a 2 and have to change them both?


Because it'll take twice as long to clog?


Don't think so. They'll both clog in approximately the same
amount of time... if the same amount of gunk is trapped in them.

And even if they *do* take twice as long to clog, what have
you gained? You have to have two pairs of parallel filters
or shut down, and change two filters, and carry two
different sizes of filter on board.



If you really want to set up your system to not have to
change fuel filter elements, then just don't have one at all
and rebuild your injection system annually. Wouldn't that be
easier & cheaper??


You've assumed he's a diesel user, but when someone uses the phrase "gas
tank" I assume it's gas.

We're assuming different kettles of fish.


Not if it's a fuel injected gas engine. If it's carburetted,
then a filter is not anywhere near as important, just a
water seperator.

DSK
jps