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Fuel filters

Tom Metzger

Sustaining Partner
There have been lots of threads about filters, and lately one starting off about fuel pumps, that referred to the filter ratings of the Universal diesel fuel filter. Most of the info reported is hearsay and peaked my curiosity.

Because I found it difficult to find ratings I believed, except for the 10 micron Wix 33390 (NAPA 3390) I started emailing Universal/Westerbeke “master” distributors asking if 10 microns was the recommend filtering level and if they recommend 30 microns for the Racor primary filter.

My distributor in the Northeast, Hansen, didn’t reply to my email. Some days later I asked a couple of others, one in Florida and one in California and got responses that I didn’t trust.

Today I emailed Westerbeke and got an interesting answer.

Hello Tom,

10 microns for the on engine spin on filter is fine. Do not go any smaller in micron rating. Our #298854 spin on is rated at 25 micron. Stay with 10 micron in the Racor as well. You want the Racor to be doing the majority of filtering.

Kind Regards,

Westerbeke Corp.”

This does not support the conventional wisdom that the engine mounted filter should finer than the primary filter. It does support my feeling that the engine fuel filter doesn’t need to be changed very frequently.
 
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ted_reshetiloff

Contributing Partner
Very interesting Tom. I use a 10 micron on the racor and always thought the Universal spin on was a 2 micron. Now it sounds like it is in fact 25 micron. So what would be the point of a 25 micron filter down stream of a 10 micron filter? Maybe 25 is good enough and we should be running 30's in the racor? They would probably last longer and would the fuel system really be bothered by something smaller than 25 microns? I wonder what the diameter of the injector nossle is? Thinking as long as thats not getting clogged why not burn the crap?
 

rwthomas1

Sustaining Partner
You can almost never have enough filter. The problem becomes pulling the fuel through an ever more restrictive filter media as the micron rating is lowered. In this case a larger filter is better. More filter media allows more fuel to flow and so less restriction. AFAIK, filter ratings are nominal. This means that no filter catches ALL particles below the stated rating just most of them.

Fuel injection parts are built to extremely fine tolerances. Its not just if the particles will "fit" through the orifices or not. Its about abrasion as well. Keeping the fuel as clean as possible will only benefit your engine.

That said, I have never had a problem with any of my diesel vehicles and the stock fuel filters. I think I am using a 30 micron in the old Racor and whatever the Universal filter gives. It works.

Ted, did you ever get that fuel pump I sent you? Just curious. RT
 
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