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What's the REAL difference between paper and stainless steel oil filters?


grayracer513

Paper and mesh filters take a fundamentally different approach to filtering. Mesh filters filter down to a certain size, and for practical purposes, no smaller than that. They do, however, only require a single pass to filter to that level. They work by simply having a very strictly controlled mesh size, through which a spherical object larger than that size cannot pass. They are rated in "absolute" terms, as with the Scotts (35μm "absolute"). This rating tells you that nothing larger than 35μm (35 microns) will pass through it. (1 micron, or micrometer more correctly, is 1/1,000,000 of a meter, or 0.001 mm, or 0.000039")

Mesh filters are able to achieve this level of filtration with remarkably low resistance to fluid flow as well, which in the case of the Scotts means that the bypass valve will not open on cold starts, and there will be no appreciable pressure loss across the filter.

SCOTTS_SS.jpg
Scotts Performance Stainless Steel Oil Filter


"Paper" filters are different. They can stop even finer debris than mesh filters, but they also allow some larger debris to pass. They filter somewhat the same way a thick shrub catches objects thrown into it. Most tennis balls get stuck, but not all. An occasional golf ball gets caught, but an occasional soccer ball passes through to balance that out.

HF154 Oil Filter 2015_02_26-scr.jpg
HiFlo Filtro Paper Oil Filter

The random arrangement and density of the fibers in the element create odd and irregular gaps through which debris can pass. This creates little crotches of sorts that enable the filter to catch extremely small debris, but also creates gaps that allow it to pass ridiculously large material at other times. The paper element media is also three dimensional to a degree, whereas mesh is essentially two dimensional; if something passes through one opening in the mesh, it's through, which isn't necessarily the case with fiber media.

Fiber, or paper, filters can stop debris as fine as 20 microns, or even less. But, they won't stop it all on the first pass. Worse yet, they won't stop all of the debris even as large as 90 microns or more on the first pass, and some particles occasionally come free of the filter to re-enter the oil stream. They are considered multi-pass filters, which carries the expectation that the same debris will pass through the system multiple times before being intercepted. They will be given "Beta" ratings like "80/25", which tells you that it will stop 80% of all 25 micron particles on the first pass. However, they will rarely publish the fact that they may very well also test at 85/35 or 85/40, and certainly will not mention that they tested at only 95/60 (95% of 60 micron debris).

Additionally, paper filters resist oil flow, particularly when cold, a great deal more than does mesh, and cold starts often cause a paper filter to bypass. In the Scotts filter, a one inch square of the mesh media they use will flow 1.9 gallons of cold 90 weight gear oil per minute at only 1 psi pump pressure (70 degrees F). The YZ filter contains about 15 sq/in of mesh, which means that the media itself has the ability to flow over 28 GPM of cold 90 weight at 1 psi. The pump at the corner gas station is less than half that fast on a good day. That figure is also far beyond the delivery capabilities of the engine oil pump in any case. That basically means that unless you run half a shop rag through your engine, the Scotts filter will never bypass under any conceivable circumstance, and will filter at full capacity regardless of temperature. This is often not the case with "paper" filters, which commonly open the bypass valve during warmup operation.

So, it isn't a black and white, indisputable, one's better than the other kind of choice, but in my opinion, the 35 micron stainless mesh is the way to go, and Scotts makes the best example of that type of filter. Let me also point out that there is a huge difference between the medical grade stainless steel mesh used in Scotts filters and the OEM brass screen filters used in YZF's up until '03. The brass filters will filter no finer than 70-80 microns absolute, which is not nearly acceptable, IMO.

Paper filters are vastly preferred by race teams because stainless filters do not capture water, but paper filters do catch water. Water is the number one engine lube problem and always condenses into the oil as it cools down and from storage. The issues with water vapor condensing are much harder on an engine, than a short filter bypass in very cold weather start up conditions. Paper filters should be changed at every oil change, not because of solid debris, but because of the collected water that they absorb.


What's been your experience using either of these types of filters? Are you firmly in one camp or another and if so, why? Does your experience conflict with anything I've written? Please do hit me up in the comments section below!

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stainless filters, flow much better, the zip ty husky teams supposedly use them, I have read bench testing that says the flow rate is so much better and the fact they can use them over are reason enough to use. I have used these longer than I can remember, I'm 61, and have put a lot of miles on a lot of bikes. my old beemers only had a mesh screen and lasted well over 100,000 miles, the old hondas same thing, I still have an old 80's honda 3 wheeler with only a mesh metal filter, it has been used forever. early engines that were well made, never had paper filters, but they are a big dollar business.

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This topic has bought about some interesting discussion and as always, claims of fame to knowledge or Superior information and as usual "but I've always done this and the race car guys do this or that" etc etc. 

Questionable comments iv'e seen already that really need to be thought about: These topics could make or break this argument!

Throwing out figures of flow rates.

If the paper filter flow rate works within the range the engine was intended then the higher flow rate is puffing smoke up your bum. Its worthless performance increases in other words. if you want to throw more expensive stuff at your bike, good on you but remember to clean that filter out before you refit it. It might be cost effective to refit a filter but i'd rather fit a new, clean one. 

  

Measuring the size of particulates that can get through a paper based filter vs a stainless filter.

How many bloody engines are in use today,  that do many many miles with paper filters and they have no engine trouble in relation to oil filter failure? That is not to do with installation or lack of changing oil and filter. Not many.

 

Stating that oil can bypass the filter.    

My bike runs a dry sump and oil cannot bypass the filter because it must run through the filter based on the oil rings around the housings & the oil flow chart in the workshop manual sitting on the table in front of me. Period, the oil goes through the paper.

 

Leaving the cleaning of the stainless steel encased filter up to the standard of the person cleaning it.... Need i say anymore.

 

While i appreciate that some people prefer the stainless this is the judgment i have made. 

My owners manual states an oil change is due at (X) miles or kms but i change it way more often with oil & new filter each time.

The bike i ride, i bought new, so i'm sure it has not had anyone else mess with the engine, other than the dealer who loaded it with twice its recommended oil amount, dry sump filling error that tricks all the newbies. 

The bike i ride has a world reputation of an easy 5000 kms before it even needs a piston (high performance 4 stroke enduro) and even then at 5000 kms people report little to no wear.  

Modern bikes treated well with care are perfectly capable of the task with a standard filter, good grade oil and regular oil changes. Throw in a magnetic tip sump plug & this will help collect anything you don't want floating around.

 

This is like arguing a $600 (Z) rated tire is way better and worth the money compared to a $300 (L) speed rated tire when we are fitting this tyre to a Suzuki Jeep capable of 90mph max in a country with a speed limit of 110 mph. Yes your (Z) rated tire is amazing but you've also got the student fitting it (potentially the guy cleaning out a filter in our case) and you'll never see the benefit in the real world if the (L) rated tyre is used for the purpose it was designed. 

(I'm an automotive tutor in New Zealand. I've been a technician for VW Audi Peugeot Nissan Suzuki & general brands. I hate getting into debates with engineers because the figures and statistics, science physics are only good if they apply to the argument and are presented in a way people can understand otherwise they are "look how cleaver i sound" remarks).    No offense to the engineers, I have spent my career working around engineers mistakes & trying to remain profitable while doing so. These are engineers designing vehicles worth hundreds of thousands of dollars.

Point of interest, When i left Audi a few ago. Many new models had a plastic sump with a fake plastic sump plug. If you undo this plug you will smash the sump open & be removing the engine. the oil is extracted by inserting a vacuum tube down the dipstick tube (it doesn't have a dipstick either) Rather read on the inboard display. Then you spend 10-15 mins sucking the oil out from in this case, a modern v6 twin turbo engine. Yes, With a paper filter. Just saying. And yes, not all the old oil will come out... Thanks to the Engineers!    

 

I'm not debating that SS filters are not as good.      

But if you don't clean it 100% as good as a new filter you might a swell use paper filters with regular changes.  

Save your money from buying the stainless filter and use a better quality engine oil or change it more frequently.  

 

Thanks for reading my 2c worth, and don't upset the engineers, they come in handy when you need to borrow a deburring tool or likewise. 

Edited by surfez
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I don't think he realizes that the oil can bypass the filter element within the filter canister. It does not need an external bypass.  This internal bypass often happens on a cold engine with cold thick oil, it takes trapped dirt and moves it into the oil supply. Use a multi weight oil, it will help. 

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I have never replaced an oil filter since I've owned my bike.  It came with SS filters in it.

Photos from my oil change this afternoon.

IMG_20181104_162559382-M.jpg

IMG_20181104_162609290-M.jpg

Rough calculation, i've saved about $500 in filters since i've had the bike.

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6 hours ago, SnowMule said:

I have never replaced an oil filter since I've owned my bike.  It came with SS filters in it.

Photos from my oil change this afternoon.

Rough calculation, i've saved about $500 in filters since i've had the bike.

I'm assuming that you've at least cleaned it!!!

One thing to figure into the cost of SS filters is brakecleen or whatever you use to clean the filter.  Not much, but an additional cost.  I personally love my SS filter, and in the long run will definitely save me a lot of money...

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I have run Scotts since they came out with them. Every bike I get gets one right away. 

Started with the BSA singles, had them make filter [Scotts will custom make a filter] for vintage era Triumph Trident external filter housing [vintage Trident owners its my fault they are available 👍] . BSA had gear pumps, did not want any flow restriction, it was installed on the return side.

Anybody talking how hard, crucial they are to clean . . . . . . has never owned one or cleaned one, spreading "fake" internet rubbish.

I clean them in small Glad container and kerosene, just swizzle it around not submerging it, followed by 40 to 50 psi air blowing inside to out. I re-use the kero next time. 

The thing that takes the longest is if and when I want to look at the particulates. As said before, cleaning every 5th time more than adequate

www.harborfreight.com/magnifier-head-strap-with-lights-38896.html. This is a genuine H.F bargain. You will not know how you did without.

Anyway run whatever you want, just put em away wet . . . . . with oil.

I never bought a motorcycle to save money, and I do enjoy spending it on them:ride:

 

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Centrifugal filters on current Honda models like the 230 don't catch water, I suspect they probably don't filter small low mass particles well either. These types of bikes are not high tech, high performance, tight tolerance machines and apparently don't need a paper filter to last a long time, even the the big bore, stroker, hi comp builds are very reliable and get beat on consistently for years with out suspected oil corruption wear problems.  I'm not sold on SS filters, I don't ride enough to warrant them and paper filters haven't caused any harm so why change now? Oil pumps have been designed to use them with the understanding of the flow through them. More oil flow is better, sure it's more functional than just lube is a coolant as well,  more circulation should lend to better cooling benefits until saturation, but is that beneficial enough? I've not seen testing to make a conclusion.

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Nothing like an attempted friendly sharing about the holy lubricant to bring out the GD scientist molecular biologist in everyone.  For those that think politics are partisan, they've obviously never strayed into the dojo of lubrication that shall not be given name.

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I used to use stainless re usable filters on my ktm 450 after 3rd crankshaft seized I switched back to paper.If u own a KTM be careful, the brass bushing that the rod is on can seize because of lack of oil flow on startup

 

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I love the idea of SS filters, but one thing keeps me with paper filters....
"disintegration".  If the paper filter breaks down, paper goes through the engine.  If the SS filter somehow breaks, metal goes through the engine.  Better to have paper go through the engine.

-My opinion.

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I thought the condensated water will escape the case by way of the case breather in the form of steam after the bike warms up?

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