I have been pouring over the interwebs about diesel filtration. There is a lot of information about this subject but a few things are unclear. The primary filter is before the injection pump and injectors and only filters out the big chunks of stuff. The secondary filter does all of the heavy work like small particles and water separation. It seems that most of the particles make it to the injectors before being cleaned out through the secondary filter. If water and contaminents are so bad for our engines why do we not see that many failures due to water? it would seem that water would be ingested before it even makes it to the filter? Also it seems other makes such as ford and dodge have much more sophisticated filters than say my OM617 and my car has survived 28 years of OE equipment, does it really mean that fine filtration isnt as necessary as widely believed to be? Would I see any beneficial gain to adding a more elaborate filter setup as Ive seen done to my engine or is it really not necessary? Thanks

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual