You can always check with Universal.
I believe that the on engine recommended filter #298854 is a 10 micron filter not a 2 micron. Looking up the cross reference filters with the above part number, they are identified as 10 micron filters. Looking at the M25 engine manual no spec is stated.
From a practical standpoint the 10 micron filter (in my opinion) is more than adequate to keep the harmful fuel particles out of your engine.
It appears the stock on engine fuel filter might be a "25 micron" but we could really go down the rabbit hole with micron ratings. The problem is it is hard to compare one manufacturer's rating with another's.
Here is some interesting old stuff from Maine Sail, AKA RC:
Re: On to the secondary fuel filter!
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Reply #2 on: July 26, 2011, 12:47:34 PM »
If you want to go aftermarket I like the Wix, Donaldson or Baldwin filters. The factory filter is approx a 25 micron, "absolute" according to Joe J. at Westerbeke, and the Kubota, according to my local dealer, is a 24 micron (but I have never heard of a 24 mic paper).
That being said we have no clue what the filtration efficiency is for the factory filters so that 25 micron filter may be at 98%, 99% etc. and would possibly be a 10 micron filter at 50%.... So, it still could be a 10 micron rated filter if you look at different efficiencies.? I do know that Westerbeke on engine filters are 15-17 micron rated and Westerbeke actually publishes this..
If you want to take advantage of multi-step sequential filtering, the primary taking some load and the secondary taking some load, a 30 mic on the primary and the good aftermarket or factory is a fine set up. If you have clean fuel a 10 mic on your primary will be fine and your spin on will catch virtually nothing as it is may already be filtered out beyond that spec. Parker / Racor filters are rated nominally at 95% efficiency so the 10 micron is theoretically capturing 95% of the particles at or bigger than 10 micron.. They consider "absolute" 98.6%-98.7%..
Universal advises against anything smaller than 10 mic for the spin on, though I don't believe you could even find one and of course we don't know if this is absolute or nominal..
Kubota apparently designed this product to run on 25 micron "absolute" filters, but at what efficiency we do not know, so over filtering to 2 micron is not really all that necessary.
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Last Edit: July 27, 2011, 11:59:07 AM by mainesail »
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-Maine Sail
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Reply #5 on: July 26, 2011, 02:50:59 PM »
The problem with equivalents is they are rarely equivalents. The Wix for example is a 10 micron nominal rated filter with no definition of what "nominal" is for Wix. They don't know the "absolute" as I have spoken with their engineering department to try and find that out. The Universal is claimed to be a 25 micron by Joe J. at Westerbeke and the Kubota a 24 micron and some others like Donaldson a 17 micron etc. etc...... Fram simply chooses not to publish any micron specs for the "equivalent" filter? It is hard to know what the equivalent is when it is tough to get a straight answer out of Universal.
Slight changes in micron ratings with oil are one thing but with fuel it can mean injector issues which can get expensive. I suppose so long as the "equivalent" filter is less than the micron rating of the Kubota or Universal filters you should be fine. Of course even my local Westerbeke distributor does not know what the factory micron rating is. I had to email Westerbeke to find out and was told 25 micron "absolute" but as I mentioned above depending upon the efficiency rating it could still be a 10 micron "nominal" filter even if a 25, if that makes sense..
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Last Edit: July 27, 2011, 11:52:46 AM by mainesail »
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-Maine Sail
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Reply #11 on: July 27, 2011, 05:58:37 AM »
I have emailed & called a number of manufacturers of filters to see if we can get to the bottom of this. As of yet only a few have responded.
Quote from: Baldwin Filters
"RC,
BF940 has a 4 nominal with a 15 absolute micron rating.
Thank you,
Sandra H."
I also re-confirmed with Westerbeke tech support in Taunton, MA, 5 minutes ago, that the on engine 298854 is a 25 micron absolute rated filter. Joe J did not know what the nominal rating of the 298854 is...
Quote from: Donaldson Filtration
RC,
The P550127 filter that cross references to your Kubota filter has a 17 micron absolute and 5 micron nominal rating. This filter fits a large number of applications and may not match Kubota's micron specifications exactly. I don't know what the Kubota filters are specified to.
Thanks
It should be noted that Donaldson defines "absolute" as 99% of the particles trapped to 17 micron...
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Last Edit: July 27, 2011, 10:28:42 AM by mainesail »
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-Maine Sail