I believe the FASS System has two filteration options. 10 Microns & 3 microns. Personally, I would go for the 3 microns.
A number of the diesel engine manufacturers are entertaining the ideas of finer filteration for the fuel systems. The HPCR systems seem to be more susceptable to damage from dirty fuel and fuel with low lubricity. Caterpillar, for instance, is now filtering down to 1 micron. Chevy/Duramax has just come out with a dual-element filter, made by Racor, that filters down to 7 microns in the outer filter media and 3 microns in the inner filter media.
There are a number of people on the Dieselplace.com (Duramax) website building aftermarket fuel filter systems using the 1 micron Caterpillar filter. Fleetguard has been filtering to the 10 micron level but, now has some filters filtering to the, I believe, 5 micron level. They seem to be showing some interest in finer filteration. Cummins is aparently "looking into the issue", also, I've heard.
I don't know if these large company's are just taking "a shot in the dark" at fixing the fuel delivery issues or, their research has shown this "is" the fix.
On the other side of the coin, there has been some suggestion that finer filteration presents it's own set of problems. #1, The pump having to work too hard to suck the fuel through such a dense filter. #2, The filters "loading-up" very quickly because they are filtering so much "crap" out of the fuel. I think I'd rather have to change the filter prematurely than the fuel system. I've, also, never heard of a pump failure because of too dense of a filtering media. However, I could see how that could happen.
I installed one of the 1 micron Caterpillar filters on the 115 gal. aux. fuel tank on my truck and towed my trailer, for the first time, going to May Madness. I was, especially, concerned about how it was going to work pulling a load and working the engine hard. So far as I could tell, it worked just fine. The Cat filter is huge! Probably, 12"-14" long. Looks like it could hold a shovel-full of dirt.
I noticed that you live or work on a ranch. If you are using a bulk fuel system and only get fuel from that system, you could put a 1 micron filteration system on the bulk storage tanks and filter the fuel for all your diesel equipment. Just a thought. I ran across a guy, George Morrison, back east that does that and has never had a problem with his Duramax while many other Duramax owners have been having problems.
While I'm no expert in these matters, I have been having some injector issues with my '03 and have been doing some reading about ways to possibly minimize these problems. Just thought I'd pass-on a little of what I have heard. Hope it helps.
Joe F. (Buffalo)