10 micron versus 2 micron fuel filters

10 micron versus 2 micron fuel filters. It seems a no brainer to me. The PO left of box of 7 ea 10 micron and 2 micron fuel filters for my Racor 500.

Why would I ever use the 10 micron???
What am I not understanding?

I also added a Racor 900 fuel polisher using 2 micron filter. Since I ended my trip, I've been running that whenever I'm on the boat. I'm up to about 5 psi vacuum now, so will also change that today.
Will change engine filters today also (2 micron Purolator F50149).

Engine oil filter is Napa 1806. THat will be replaced with ??? Fram 2821A

Comments, thoughts, suggestions.

I've been dragging my heels on this for 2 weeks now, so I've reached apoint that some action is better than nothing.

Richard

Richard, IMO, if you have 2 fuel filters in series as most do, the 10 micron filter should be first to catch the water and larger particles and the finer 2-3-5 micron filter second to finish the job.
My understanding is that most pleated paper engine oil filters are 7 microns regardless of mfg..
Vacuum is usually measured in inches (of mercury or water) not psi, so I'm not sure what you are asking there.

Brooksie said:

Richard, IMO, if you have 2 fuel filters in series as most do, the 10 micron filter should be first to catch the water and larger particles and the finer 2-3-5 micron filter second to finish the job.
My understanding is that most pleated paper engine oil filters are 7 microns regardless of mfg..
Vacuum is usually measured in inches (of mercury or water) not psi, so I'm not sure what you are asking there.

Click to expand...

Sorry, I meant 5 inches of Hg.

The two Racors (select one or both) feed the two engine mounted filters.

I have only run 2 micron in my last two boats with thousands of hours on them and many thousands more on the commercial boats I run.

Only once did I have a filter clog that forced me to shut down and change filters underway.

If I had allowed any fuel to sit or go bad for any reason...maybe I would have had more occurrences.

That said...keeping a few 30 or 10 micron aboard in case you ever got bad fuel or developed a fuel problem may not be a bad idea.

psneeld said:

I have only run 2 micron in my last two boats with thousands of hours on them and many thousands more on the commercial boats I run.

Only once did I have a filter clog that forced me to shut down and change filters underway.

If I had allowed any fuel to sit or go bad for any reason...maybe I would have had more occurrences.

That said...keeping a few 30 or 10 micron aboard in case you ever got bad fuel or developed a fuel problem may not be a bad idea.

Click to expand...

SOrt of my thinking too.
I was also thinking of putting one in each. Then run off the 2 micron and if it starts clogging just switch to the 10.

Is your Racor polisher the same filter as your in-line engine filter, or are these separate elements? If the latter, I would use the 10 micron in the polisher and use the 2 micron as the in-line filter that precedes the engine -mounted filter. If not separate, I would use the 2 micron for both filters. We typically get 65 hours or more on a Cummins 5.9BT with a Racor 900 2 micron.

I did a little research on this subject a couple of years ago because it appeared the PO of Boomarang had been using 2-Micron filters in an FG500 Racor primary filter. Being a single-engined boat, I wanted the best info on the subject. I ran across this whitepaper that you might find enlightening. I have Yanmar power so I checked with the factory reps and received the same recommendations. I changed to a 10-Micron primary filter and everything just purrs.


Editors Note: This very illuminating “White Paper” started as an e-mail thread. An owner of a boat with Cummins diesel engines remarked Cummins Factory mechanic had made a notation in the log book advising the previous owner to “only run 10-micron filters in the Racor primary filters.” He was very explicit – 2-micron filters should NOT be used. There is an active urban myth about using 2-micron filters, despite the fact that most diesel manufacturers specifically advise against using 2-micron filters, advising it may cancel warranty obligations for certain types of fuel-delivery engine failures.

The following is from Bob Senter, currently with Alaska Diesel and previously with John Deere marine propulsion. He has over 25 years working with diesel engines and their manufacture.

“Regarding the previous Cummins mechanic’s note to use 10-micron primary filters, the owner should have listened attentively. He was given good information.

“The miserable urban lore of 2-micron primary filters is showing signs no of going away. I talked with Steve D'Antonio at TrawlerFest Poulsbo about this, wondering how the subject managed to get turned inside out. Much to my surprise, it seems we're both on the same page. He thinks there has been quite a lot of misinterpretation, too.

“First, and most importantly in this discussion: To my knowledge, no diesel engine manufacturer supports the concept of using 2 micron primary filtration. My inclination is to go with these company's well researched engineering based recommendations - if only to avoid warranty claims and unhappy customers. The engineers I've met are neither backward nor uninformed about boats and marine engines. Conversely, the primary requirement of boat ownership is not an engineering degree, but a checkbook.

“Placing a 2-micron element upstream of the engine predictably results in a dramatically accelerated rate of restriction and filter plugging, LONG before the normal service interval. This is often misinterpreted as resulting from a contaminated fuel tank that needs cleaning and polishing. Or, perhaps it is perceived as a need to install an on-board fuel polishing system. I'm sure local marine businesses appreciate these self-induced "service opportunities", so there's at least some benefit. (Just a tech note here: Many modern high pressure common rail diesels and even old Detroit Diesel 2-cycle engines pump over 100 gallons per hour of fuel per hour, per engine, so they do a very respectable job of polishing the fuel by themselves.)

“These days, fuel filter media is usually composed of plastic impregnated paper with millions of tiny electrostatically punched holes in it. Microscopically speaking, it functions as a colander, as in “cooking pasta”. Dirt in the fuel, viewed microscopically, is variously sized gravel. The filters' micron rating is nominal, not exact. In reality, many of the holes are partially plugged by debris in a very short time, leaving a matrix of MUCH smaller holes to filter the debris. In other words, your 10 or 30 micron primary filter turns into a much finer filter almost immediately. The job of the secondary filter is to remove most of the particles of a size that could damage the fuel injection components. Most Tier II emissions high pressure fuel system engines use a 2-micron filter in the secondary filter.

“At this point, we need to challenge the Holy Grail logic of a "single point of failure". Fuel filters are routine service items, not failure items; they don't break - most on-engine secondary fuel filters can be changed and the air bled out in less than 5 minutes. The average boat owner can't change a Racor element that fast, start to finish. If you're really serious about this argument, then you would never buy a boat with engines that have difficult fuel filter service issues. Same comment applies to primary filter physical locations.

“Engineers typically size the primary and secondary filters so that they will load up at approximately the same rate. The unspoken truth of the “single point of failure”, e.g. 2-micron primary filter concept, is that owners begin to believe that the primary does all the work and the secondary just goes along for the ride. If only this were true. Since the elements are paper, eventually, they will soften when ignored and exposed to (ever present) water, ultimately resulting in the trapped dirt and water being released downstream, contaminating the expensive fuel system components. Changing the Racor element is only half the job - you still must change the secondary filter(s) on schedule. This is not optional or subject to interpretation.

“Now, on to the myth of vacuum gauges. OK, the gauges may work properly, but the users seldom do. The only time the gauge is meaningful is at full load rated speed - this is when the problems manifest and precisely when you don't want to have problems. How many operators know the difference between inches HG (of mercury) and PSI (pounds per square inch) or what the operating characteristics of their engine are at a specific point? Long before you hit the red zone on Racor’s vacuum gauge, the fuel injection pump will experience problems resulting from restricted fuel flow. These problems could be excessive fuel temperatures in the pumps, air bubbles or hydraulic timing advance erratic operation - sometimes all three. A diaphragm type fuel transfer pump may fail prematurely when badly restricted. All of these are much more expensive, onerous problems than simply changing the secondary on-engine filter. By the way, Racor’s website has a very illuminating graph showing fuel flow vs. restriction – it goes nearly vertical at about the time the gauge needle gets into the yellow zone.

“Then there's the idea of "pressurizing the system". Placing a low pressure transfer or priming pump ahead of a 2-micron primary filter accomplishes an unexpected result: the operator goes from receiving some warning symptoms of impending filter plugging to receiving absolutely no warning at all - the engine just stops when you need it most. Personal experience speaking. I have verified this in my own boat….in front of a ferry.

“Finally, empirical testing, the basis of science, means proving your theory. When I crossed the Atlantic with the Nordhavn Atlantic Rally boats in June 2004, I counseled all 18 boat owners with exactly the same advice on fuel filters and service you've seen written here. In every case, the owners who followed the recommendations to use 10 or 30 micron Racor primary filters and change them on schedule experienced NO fuel related issues, even when they received bad fuel in Ft. Lauderdale. I also suggested they save the 2-micron elements for their fuel polishing systems. A few owners disagreed with this advice and enjoyed the experience of changing Racors in deeply rolling, diesel sloshed, and blistering hot 135 degree engine rooms. Somewhere, I read a quote I still love: "Wisdom comes with experience; and, experience comes from bad judgment".

Larry
m/v Boomarang

I drive a diesel truck and my IP (injection pump) would wear out quite frequently and I had expensive rebuilds as a result. I did a lot of research and found Stanadyne who makes the IP's said particles larger than 5 microns will wear out the plates in the pump and cause failure.

I installed two Racors and tossed the OEM filters. I placed a 1o micron first and a 2 micron second. Since that time I have quadrupled my time to replace my IP. I'm sure the injectors are benefiting as well.

It appears to me any manufacturer that says 2 microns are not needed are looking at their bottom line more than the customers wallet. Just my 2 cents.

By the way, I have 2 microns on my boat and have since finding out about wear from larger than 5 micron particles. I haven't had any problems clogging either. I'm going to always use 2 microns.

LarryM said:

!.LHGJGSomewhere, I read a quote I still love: "Wisdom comes with experience; and, experience comes from bad judgment".

Click to expand...

COULD NOT AGREE MORE!
As much as I love this forum, there are questionable posts On here that are misinformed. This subject is really a good example. Good post!

The current bible for marine engine (say less than 600HP) filtering can be found on boatdiesel.com articles and writings. As several have done on this forum and recommendation from boatdiesel - use a 3 stage setup which is 30u, 10u and on engine. According to boatdiesel, a properly setup 3 stage system will catch most water and green slime at the oversized spin on primary, which is the whole objective.

On my vessel with 10 year old tanks I use a 30u primary Racor followed by on engine with no vacuum buildup whatsoever on the primary. For low fuel flows most of us have, using 2u as primaries seems to work fine for many but as mentioned 10 works fine too. In another 5 years I'll likely go to a 3 stage - 30u Fleetguard spin on, 10u secondary and on engine - setup as tanks age.

Fuel polishing is another (black magic) subject, recently discussed on TF thread "fuel pumps." As an aside, on freshly minted diesel most/all is filtered at 30u as it feeds refinery storage tanks. My favorite fuel stops in the PNW all use 30u filters at the pump. Be careful filling from a shore truck unless you know the hauler and shipper and even at that, have a first class onboard filtering setup.

sunchaser said:

On my vessel with 10 year old tanks I use a 30u primary Racor followed by on engine with no vacuum buildup whatsoever on the primary. For low fuel flows most of us have, using 2u as primaries seems to work fine for many but as mentioned 10 works fine too. In another 5 years I'll likely go to a 3 stage - 30u Fleetguard spin on, 10u secondary and on engine - setup as tanks age.

Click to expand...

Thanks All.

So with this information, I am thinking 2 micron in polisher (this is NOT inline with fuel filters)

Then 10 micron in the Racor 500s (primary and spare), switchable to one or the another or both (I now have 2 microns in these and I had to switch to "both" to get engine to run)

Lastly the recommended engine fuel filters (Napa 3166).

I'll keep you posted.

I have a floscan and prior to the filters on the engine which is 2 micron I use a 30.

Smaller than that causes bubbles in the fuel flow which screws up the flow scan.

Cat fuel filtering...primary 10 micron...secondary 4 micron..

"

Good enough for Cat...good enough for me...​

http://parts.cat.com/cda/files/3022934/7/PEHJ0269Filter.pdf

If I had a high power, fast boat...I might worry about restriction...acceleration from 2 knots to 6.3 doesn't really pin my ears back.

To quote them all...a diesel needs good clean fuel and air. If a 2 micron doesn't clog in hundreds of hours of use and doesn't restrict flow..then using one at the same price as the 10/30 microns...then BFD.​

​

skipperdude said:

I have a floscan and prior to the filters on the engine which is 2 micron I use a 30.

Smaller than that causes bubbles in the fuel flow which screws up the flow scan.

Click to expand...

Thanks Skipperdude...never heard that but I'll add it to my inventory of diesel issues that are hard to figure out...

Did you discover it or is it a well known warning that floscan provides?

Flow scan has it in there literature same as not using teflon tape on any of the connections. Just pipe dope.

The teflon tape get into the fuel flow in the form of small threads that break off from the connections.

It is supposed to really screw a Flow Scan up.

sd

psneeld said:

Thanks Skipperdude...never heard that but I'll add it to my inventory of diesel issues that are hard to figure out...

Click to expand...

Diesel absorbs air quite easily. When you take on fuel it splashes at the nozzle and in the tank and quite a bit goes into solution. When the fuel is under a low pressure as on the suction side of a pump, the air (and vapor) will come out of solution and create a bubble. If you put a clear piece of tubing at the lift pump inlet you will probably see a bubble form after a couple minutes running. This is mostly vapor and will never get any bigger and the discharge side will show nothing since the air and vapor went back into solution.

In something like a flowscan that air/vapor bubble can really screw up the flowmeter reading since the little turbine needs solid liquid to turn proportionally to flow. Since there are two sensors on a diesel system, the return flow which has no bubbles compounds the metering error.

Thanks Rick-

I certainly can understand if the low pressure becomes great enough...never heard of any complaints from the guys I know with floscans...curious what it takes in real world numbers to become an issue...

Wxx3 said:

Thanks All.

So with this information, I am thinking 2 micron in polisher (this is NOT inline with fuel filters)

Then 10 micron in the Racor 500s (primary and spare), switchable to one or the another or both (I now have 2 microns in these and I had to switch to "both" to get engine to run)

Lastly the recommended engine fuel filters (Napa 3166).

I'll keep you posted.

Click to expand...

Richard: Why did the filter get clogged? Was this after you cleaned the tanks?

Perkins calls for 10 and final filter. I do a 30-10 two-stage and "polish" at 2 (although please read up on what the micron rating really are all about... it's not what you think). It seems like it would make more sense to follow the factory specs here. No sense making the pump have to work so hard to suck thru a 2 when it only needs a 10. But that's just me.

You guys do what you want. I already found my answer.

From LarryM's post of the "white paper"

“At this point, we need to challenge the Holy Grail logic of a "single point of failure". Fuel filters are routine service items, not failure items; they don't break - most on-engine secondary fuel filters can be changed and the air bled out in less than 5 minutes. The average boat owner can't change a Racor element that fast, start to finish. If you're really serious about this argument, then you would never buy a boat with engines that have difficult fuel filter service issues. Same comment applies to primary filter physical locations.

Takes me less than a minute if I have to....that's where this guy lose me as "an authority"....

While this is on fuel filters , did anyone else note

"A few owners disagreed with this advice and enjoyed the experience of changing Racors in deeply rolling, diesel sloshed, and blistering hot 135 degree engine rooms."

Guess ventilating the engine space to the engine assemblers specs was not part of the design?

My engine space is most definitely NOT "diesel sloshed" ....or anything else sloshed.....just saying.

Amazing that so much ignorance persists regarding multi-stage filtration. Of course Larry M's post has it right...it is the definitive answer.

Aquabelle said:

Amazing that so much ignorance persists regarding multi-stage filtration. Of course Larry M's post has it right...it is the definitive answer.

Click to expand...

Not even close...

Read Steve D'Antonio's article in Passagemaker...
Fuel Filter Micron Ratings Explained | PassageMaker

"Now, back to your mechanic’s comments. Technically, he’s right in that this is Yanmar’s advice, however, I don’t necessarily agree with Yanmar’s reasoning as to why they recommend 10 or 30 micron primary filter elements"

Steve D does believe in multi-stage but there's NO complete or even reasonable agreement as to why...and plenty of boaters running all 2 micron can verify that on low fuel burn engines...there's NO reasonable difference in maintenance and performance.

Here's from Yanmar help

FUEL HELP

"Spring when it's still cold, the 'summer' diesel will block 2 micron filters, causing the engine to slow or even stop. My experience with this was on high horsepower engines fitted with 2 micron primary fuel filters only. Fitting 10 micron filters solved the problem."

If you read it it says "high hp engines" and switching from 2 micron...yet nothing about how a 2 micron may not be suitable for all year round use or on lower hp engines.

Cummins doesn't even state what is "preferred micron rating" just that THEIR filters are OK...

": What is the difference between Absolute and Nominal micron rating?
A: Micron rating is the size of particles which are filtered out by filters at a certain efficiency. When this efficiency is at least 98.6%, we speak about absolute micron rating/filtration. Nominal micron rating is just a commercial trick for all efficiencies lower than 98.6%, meaning that for the same micron rating (for ex. 10 µ) in the case of nominal rating, not all particles will be captured in the filter as in the case of absolute micron rating. "

Frequently Asked Questions

yet here's another clip from Cummins

"Remember: 3 micron on-engine, stage 2 filters, should never be pre-filled."

Cummins Engines

So the guy from Alaska Diesel probably misquoted Steve D, can't change a RACOR in less than 5 minutes, thinks everyone has hot engine rooms full of diesel...and doesn't REALLY know what some of the BIG diesel engine manufature's recommend or really care about.

Sounds to me like a guy who has himself convinced he's right and his way is the only way....

Scott's right... He usually is.

I had a long email conversation with an engineer and VP from Balwin during my fuel project a few years ago. Here are some of the key take a way's as related directly to this thread:

My question - Why isn't the micron filtration of your filters listed anywhere? Is there something I don't know about filtration that I should know? I have two Racor 500's with a 30m and 10m filter cartridges. I was hoping to have a 2m as the "secondary" CAV filter.

Micron ratings can be fairly complex. It is imperative to know the efficiency (Beta Ratio) associated with the given micron rating. When a company publishes a micron rating without this information, it does not tell the customer how efficient the filter is at the given particle size. For instance, if Company X rates a filter at 15 micron, they may be referencing a nominal micron rating which could mean the filter is anywhere between 50% and 90% efficient at that particle size. Please see the links below for more information about the micron ratings of filters.

http://www.baldwinfilter.com/literature/english/10%20TSB's/89-5R3.pdf
http://www.baldwinfilter.com/literature/english/10%20TSB's/04-2R1.pdf

Travis R. Winberg
Manager of Service Engineering

skipperdude said:

I have a floscan and prior to the filters on the engine which is 2 micron I use a 30.

Smaller than that causes bubbles in the fuel flow which screws up the flow scan.

Click to expand...

That is my understanding,also.

Jeez,

I thought I could put this subject to bed, but after reading psneeld's post, it got me thinking that maybe the 'fuel flow vs. filter capacity vs. filter effeciency equation' needed more investigation. I decided to go back to the original Racor - Parker Hannifin documentation I used for my research a couple of years ago to see if I had overlooked anything. Lo and behold, maybe EVERYONE IS RIGHT!! 2-Micron, 10-Micron or 30-Micron - you are all correct!

Racor clearly states that "If the secondary filter has a rating of two (2) microns, the primary filter should have a rating of (10) microns. If the secondary filter is rated at 10 microns, the primary should be 30."

But later in the document they state that in a marine environment, "If the installation can allow the use of a filter large enough, then a two micron filter can serve in a system as the only filter in that system."

Interestingly, throughout the document, there are distinctions made between marine, over-the-road and agricultural usage relating to fuel quality, cleanliness and filtration.

From this I think it might be safe to conclude that adequately sized, 2-Micron filters of the proper type can be used as Primary filters. There should be no adverse effects on the lift pumps, and the filters should have a reasonable service life.

Below are excerpts from the document where I have highlighted in red the two paragraphs that at first, seem to be contradictory, but ultimately seem to support both sides of this issue.

++++++++++++++++++++++++++++++++++++++++

RACOR Fuel Filtration

Chapter 8

PRIMARY FUEL FILTRATION

Purpose

Primary fuel filters play a very important role in the diesel fuel system. Their primary purpose is to protect the transfer pump and remove water contamination. Another purpose is to protect the secondary filter from much of the asphaltene carried by the fuel (Fig. 37).

The finer the level of filtration that the secondary filter is designed for, the more quickly it will choke from the asphaltene in the fuel. A properly specified primary filter will share the choking effect of asphaltene, thus allowing the secondary to be replaced less frequently.

If the secondary filter has a rating of two (2) microns, the primary filter should have a rating of (10) microns. If the secondary filter is rated at 10 microns, the primary should be 30. It is recommended that filters which combine water separation with the task of primary filtration be used instead of a simple primary filter.

It is desirable to choose a primary filter that will provide the lowest pressure drop or negative pressure at the outlet of the filter at rated flow when the filter element is new. No more than two inches of mercury (2”/hg) negative pressure should ever be allowed when a new primary filter is first installed.

Recently (1998), many engine and fuel injection system companies have begun to recommend that the fuel injection system be protected by a water separator. In fact, suppliers of common rail fuel injection systems demand that high efficiency water removal be part of the primary fuel system. The best value in meeting this demand is to install a primary filter that is designed to separate water on the suction side of the fuel system. Water separators are discussed in detail in Chapters 9 and 10.

Filtration Efficiency

Fuel filters are supplied for various applications and, therefore, there is a need for different levels of filtration efficiency in the removal or retention of particulates. The hydraulic industry uses a rating method that uses the term "Beta Ratio" to describe a filtration efficiency level. The diesel fuel filtration industry generally uses simple efficiency as the method of rating a fuel filter. Since there is no such thing as a fuel filter that provides absolute filtration of the particle sizes that are cause for concern, the
industry uses terms like 96% @ 5 microns. This term means, that when tested to SAE or ISO test methods the filter will retain 96% of all 5 micron size and larger particles.

Racor makes filters with various filtration efficiencies, but its standards for non-OEM (Original Equipment Manufacturer) are 2, 10, and 30 micron filter elements. The actual efficiency ratings for these are 98%, 95%, 90%, respectively. Racor also makes extensive use of a 7 and 20 micron filter medium which are used to meet certain engine manufacturer's requirements for a final filter and a primary filter.

Racor’s two micron filter medium should only be used in final or secondary filters where the fuel is first filtered by a primary filter. The primary filter for a two micron final filter should use a 10 micron medium. The exception in using two micron filter in a primary filter is to obtain high-efficiency water separation, and is usually used in marine applications where the fuel supply may be cleaner but also many contain water more often. If the installation can allow the use of a filter large enough, then a two micron filter can serve in a system as the only filter in that system.

The new high pressure common rail fuel injection systems require high efficiency in removal of small particles. The requirement is 95% for three micron particles. Racor fuel filters have a medium designed for these applications. Replacement elements should state, "For Use With Common Rail Fuel Injection Systems."

Dirt levels in fuel also direct the level of efficiency required. Since the filter removes a percentage of dirt particles, it follows that when a much greater amount of dirt is present in the fuel, a greater number of particles will pass through the filter. Diesel engines used in earth moving or agriculture should use fuel filters that have higher efficiency than those for over-the-road or marine use.

++++++++++++++++++++++++++++++++++++++++

This publication is 68 pages long and is worth downloading and reading, or at least keeping as a resource.

Parker Brochure No. 7550

OK, now I don't know what filter element I will use next time I change my own filters. 56hp, how many gph, yada yada yada . . . .

I'll worry about this another day. I'm going boating now!! Have a great day all.

Larry
m/v Boomarang

skipperdude said:

I have a floscan and prior to the filters on the engine which is 2 micron I use a 30.

Smaller than that causes bubbles in the fuel flow which screws up the flow scan.

Click to expand...

Skipperdude,

I found this in a whitepaper.

"Pressure drop through a fuel filter or water separator is a function of flow rate vs. the restriction of the flow path through the unit. The pressure drop on vacuum side installations is very critical due to the vaporization
or boiling point of fuel."

"Diesel fuel begins to vaporize at a negative pressure as low as 10 inches of mercury if the fuel is hot. Vapor in the fuel is related to the term “fuel starvation” and the lack of solid fuel will result in poor engine performance
or actual engine shut down."

It would seem that this same vaporization, if present, could cause problems with your Floscan sensor. Is it possible that your primary filter is not large enough, or perhaps you have a small air leak between the primary filter and the lift pump that only occurs at higher vacuum levels. Have you measured the vacuum level after changing the filter cartridge? Even with a 30-Micron element, when new, it should always be under 2”/hg. according to Racor.

OK, this time I really am going boating . . . . outta here.

Larry
m/v Boomarang