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Oil filtration

Oil filtration

Oil filtration

Anyone have any idea how well automotive oil filters work?  Smallest particles removed, removal vs size, etc?

I've had a discussion recently which called into doubt the usefullness of oil filters as a whole - the idea being presented was that since the oil film thicknesses at various key locations in an engine are often less than 5 microns thick, and since most oil filters pass particles much larger than that, what's the point of having these filters at all?

I don't wholeheartedly believe that argument, but I'd like to hear some others' comments on the matter.

as always, thanks in advance.

here's an interesting article I found, which relates slightly to this discussion: http://mr2.com/TEXT/synth_oil.txt

RE: Oil filtration

Most commercial filters take out about 20 micron sized bits.  The better(I use that word advisedly) are rated at around 10 microns.  An Oberg filter will take out 5 micron bits they say?????.  I've used Obergs, seemed OK, never saw anything in them except after a blow up! (frequent, unfortunately).  All my antique cars are filterless and they seem to do OK. I just change the oil more frequently, and , of course, they don't see the mileage and speed of modern engines. In the racing engines, I have always been more concerned with flow rate, pressure drop, heat transfer etc, and not so much about "dirt".  I cut open the filters on several engines to see what was trapped.  Not much. Mostly carbon/varnish/sludge.  On the race engines the filters were like new.  The brand of filter makes a lot of difference as to the amount of filtration v pressure drop is concerned.  Currently I use WIX filters exclusively.

As another thought about filters, in January of 2000 I rebuilt the Model A's engine(never had a filter). The bearings looked OK, considering they had 100,000 miles and 70 years on them.  Very little to no scoring???????? I had just run out of shims and couldn't tighten them up any more!  The new engine is machined for bearing shells both main and rod.
Now on the Mini Cooper, I'll let you know as I am VERY concerned due to the gearbox sharing the engines oil!


RE: Oil filtration

it is the big chunks that the filters are after.  I had a bug with a screen that had holes about 1/16"... I don't believe it stopped much, I never saw anything caught there...

I have a '01 BMW and I am almost due for my first oil change at 15,000 miles!!!  It seems a little absurd, but Porsche and several others are using the oversized micromesh filters and going 10,000+ miles between changes.

Here's something I have always found intriguing - Frantz oil filters.  This whole mentality cause me to lose sleep the first night I heard about them.  A secondary slow filter process that processes less than 10% of the oil that flows through the pump using a cellulose filter.  The basic setup that I have run across uses TOILET PAPER!!!  This seems ludicrous, but I spoke with one of my most trusted and knowlegable professors(PhD MechEngr) and he totally believes in them.  He has one on his Model A.  Filtration level = 1 micron... smaller than cigarette smoke.  We did some math and the best equivacle description that we could come up with was that the particle size equaled out to the standard engine having its oil changed every 15 minutes.  This is starting to sound like an infomercial, but I can't believe these aren't more popular.  I actually saw one of these for sale on eBay for a Corvair.

RE: Oil filtration

If you check out the last few paragraphs in the article I linked to (original post) they seem to discuss something like what you're talking about.

RE: Oil filtration

There is no point in going over all this again. Go to the  " AUTO LUBRICANT ENGINEERING" forum and read the posts there.  It's a small forum and you can go through ALL the posts in short order.
To put it briefly, the bypass filtration idea with  toilet paper is one of those 'urban legends' perpetuated by well meaning but none the less miss informed individuals including some well papered engineers. I used this system   when I was a kid and , looking back it was a joke, a very MESSY joke. As long as there are folks out there  willing to accept as fact all these off the wall ideas, there will be hucksters willing to sell them. It's the American way!  If you want a bunch of toilet  paper fibers running around in your new BMW, I have no problem with that but, I have been at this game a long time and you  won't find anything but the VERY BEST filters in my cars and trucks!


I'm suprised you haven't joined the Automotive lubricant engineering forum.  Go there and get BOTH sides of the argument before making a judgement on the 'toilet paper' filter idea.


PS---Using a roll of toilet paper to filter oil on a Model A with its .003" to .004" or more clearances and non pressurized oiling system is a FAR CRY from an 01 BMW or my 01 Lincoln LS with  .0005" clearances!!!!!!!!

RE: Oil filtration


To answer your questions, here is a "short-course" on today's oil filters:

There are two general categories of oil filters on the market today: "Full-Flow", and "Bypass" filters. I'll discuss bypass oil filters shortly.

FULL-FLOW OIL FILTERS: Your primary oil filter is a full-flow filter through which all the oil passes.

There are basically TWO types of "full-flow" filters: "Surface" full-flow filters and "Depth-media" filters. Most surface full-flow oil filters are made of treated pleated paper. They filter particles in the 20-40 micron range, essentially removing only the "bowling balls" in wear particles and contaminants. Surface filters are quickly saturated with particles however, so their holding capacity is limited to around 3,000 miles after which the oil goes around the filter through the built-in pressure relief valve.

"Depth-media" full-flow oil filters are packed with a variety of materials including cellulose, synthetic fibers, and glass fiber media. They filter acrosss the entire body of the filter and so have greater holding capacity and efficiency.

**One company makes a high-capacity, depth-media full-flow filter using all three media above, that filters out contaminants down to 10-microns in size, much better than the 39 micron filters most stores sell.

**Since 60% of engine wear is caused by particles in the 5-20 micron range, it is essential to use oil filters that work in that range if you want to reduce wear.

BYPASS OIL FILTERS: These are additional oil filters which "super filter" the oil on a partial flow basis. Since they typically filter out particles finer than 5 microns, they do so by continuously filtering only a portion of the oil on a bypass basis; typically in 15 minutes of driving at 45 mph, all the oil is filtered down to the filter's rated size.  It is important to get have bypass filter media that is "non-chanelling", that is impervious to high-pressure oil cutting a channel through the media thus short-circuiting the filter.  

**One company makes a high-efficiency Bypass oil filter that filters out wear-causing particles down to one-tenth micron!

Additionally, a "dual-remote" filter system is available for almost any car that places both the full-flow and bypass filters together in one manifold for ease of change.

I hope that helps in your quest for better oil filtration and reduced wear.

Finally, I would suggest that you try a top-line synthetic oil with the finer oil filters since petroleum sludge will quickly clog the finer oil filters.

** One reputable company makes a top-line synthetic rated at 35,000 miles or one year between changes with a filter change at 15,000 miles or 6-months.  

I hope this has answered your oil filter questions.

Best regards,

Will Miller
NOVA Engineering & Consulting

RE: Oil filtration

  What you thing about a dual filtering priciple: centryfugal and full flow. My opinion is that is possible to make everything but only production cost is important. More, chemical degradation is verry important and harmfull for an engine. I'm not in accord with 10k.miles dead line for a oil change.Poissoning with fuel is an other problem that must be analyzed.On my opinion at this time oil  filtering problems are complexes for modern engines (with verry small gaps between moving parts)but easy and shure is to remove the oil every 5000 miles and to use high quality oil filters.
Sorry for my poor english

RE: Oil filtration

comnean, your English may not be perfect, but your logic as far as  oil changes go is 'right on'!


RE: Oil filtration

   Because the subject is verry interresting, what opinion we have about presurized separate oil tank (race or F1 technical solution) At my opinion to introduce this modification for a street car is verry expensive.Or what opinion we have about special liquids like DURA-LUBE or russian UNIVERSAL IMPROUVER.
Sorry for my english.

RE: Oil filtration

comnean, I guess the best thing for you to do is to start reading some of the older posts in these forums.  Over the last couple of years we have discussed these additives at length.  My personal opinion (my race team was sponsered by one of these 'additive companies')---by and large they do not help performance.  Solid additives can and sometimes are removed by filters and of  course oil changes.  Graphite, MOS2, PTFE etc. used as lubricants leaves me wondering. Clorine is a great friction midifier but VERY corrosive in the long haul.
What I am trying to say---The  motor oil industry is VERY competitive and if the additives worked as claimed then the major mfgrs would be using them!!! Slick 50, DuraLube, CD2 , Rislone, Wynn's Friction Proofing ---ad naseum.

As to a dry sump for a street car---it has been done on the 'high end' cars but to no great advantage.  It is easily accomplished at fairly reasonable cost.  I just do not see it as an improvement over conventional wet sump designs, at least for the street.


RE: Oil filtration

I thing you have right Evelrod but I'm interresting in not suplimentar particles aditives. I know all described by You, but I' interrested by special molecular comportament. A few aditive makers have experince with a "spring" molecules models.I want to know about. The principle is not new and is similar with the same used to tunellised submersibles (russian "Tiphoon" class of submersibles). In a few words a elastic cushions between moving parts is created.
Sorry for my english.

RE: Oil filtration

There are some more observations to make.

Engine builders choose their filters (size, capability, flow rate, pressure drop etc) based on the operating conditions they expect. As for pore size engine oil filters usually filter at nominally 15 - 20 micron (compare this with a diesel fuel filter that can go down to 1 micron!) This actually means that the amount of particles smaller then 20 micron does not build up to a kind of grinding fluid during normal service and therefore a finer filter does not really contribute to less wear.

On some designs a supplementary bypass filter is used to protect parts that are susceptible to wear due to smaller particles. You will find a for example find an extra filter just before the turbobearings of Scania diesel engines.

The use of centrifugal filters can have some advantages: they do not rely on particle size to be effective but rely on the effect of gravity and therefore are able to filter out very small particles (and leaving the oil additives where they belong - in the oil that is).

There have been investigations on the effect of pore size. Steyr published an SAE paper some years ago stating that finer filters do not have the effects that are claimed by some filter manufacturerrs, simply because the particles they try to catch are not there in sufficient quantity to cause increased wear anyway.

Further you should be aware that the size of particles that do cause wear depend both on the amount present and their relative size related to actual clearances in the engine.

The last few years we have seen an increase in oil drain intervals. If you compare the filters used on these new designs you will notice that filters have somewhat increased in size (and thus in "dirt stacking capacity" and not in pore size.

To sum it up: just stay with the engine builders recommendation if your operating conditions are within the range envisaged, when you are operating the engine outside that range supplementary filters might be of interest. In that case you problably better contact a reputable filter manufacturer to seek additional advice.

RE: Oil filtration

Isaac, back to your original question---You know I don't generally tout one brand over another.  I usually leave that to the individual, you know, 'different strokes for different folks'!  In this case I will make a small exception---Of all the brand name filters I have at hand some are just simply built to a higher standard than others.  Just ONE example that you can perform at little expense---Cut open a Wix oil filter and a Fram oil filter for the same application, say a Wix 51515 and a Fram PH-8A and tell me what you see.


RE: Oil filtration

51515 - that's fits a Ford 302, right?  I don't remember what the "deep" version of the same filter is though...

I've cut 'em open before - used to work at an auto parts store, and we made a display out of several brands' chopped-up filters.  I used to compare all my filters in this manner after using them (ugh, messy).  I know that the Fram (standard) filters are horrible pieces of garbage compared to the Wix (light, floppy stamped leaf spring vs steel coil spring, ratty looking tissue-paper element vs heavy paper w/fiberglass, odd rubber thing vs steel+rubber bypass valve and silicone anti backflow valve, etc).  

Fram also has that other "heavy-duty" filter line that looks about as good as Wix (and sells for about the same price).  

There are several brands' filters out there that are indistinguishable to the naked eye (even have the same characters stamped into the base plate, same spring, same number of pleats, etc), yet range in price from about $1.80 to $9.80.  I don't remember the brands right now, but next time I change the oil I'll refresh my memory.

RE: Oil filtration

   Y thing that chemical transformation are verry important because at the day performance is possible to filter everything. But! chemical modification is ireversible and imposible to filter.In a engine big oxydation phenomena are present and a acid oil is harmfull for the engine (all metalic parts can suffer from a acid character of the oil).

RE: Oil filtration

Like I have said (about a million times, ad naseum)---
CHANGE YOUR OIL AT REGULAR INTERVALS, say 6000 miles on most newer cars and 3000 on older and turbo cars.  I change at 1000 on my antiques (they have NO filters).
Changing the oil eliminates all the contamination, acidity, grunge and grime.  You get a fresh oil additive package at each change along with piece of mind!  Filters are great and as COMNEAN says " (it) is possible to filter anything" .
In these forums we have determined that regular  oil service IS NOT YOU MAJOR AUTOMOTIVE EXPENSE!!! A  little common sense will take you a LONG way in this.


RE: Oil filtration

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