Engine Oil Filters Overview

[ Recommended Filters | Filters To Avoid ]

What Makes A Good Filter?

Engine oil filter have one purpose in life: to filter out the particles that enter the oil so that they don't act as abrasives when the oil recirculates.  The filter is a cellulose (paper) or synthetic media that is usually contained in a steel can.  The front of the can typically has a threaded center with surrounding holes.  Oil enters through the surrounding holes, passes through the filter media, and exits through the threaded center.  The filters usually screw right onto the engine block using an o-ring gasket to prevent leakage.  Many filters have an anti-drainback valve to prevent dirty oil from backwashing back into the oil pan.  They also have a pressure relief or bypass valve that will allow oil to bypass the filter element in the event that it becomes too plugged to pass enough oil.  This prevents engine oil starvation and the possibility of destroying the element, allowing pieces of it and the junk it filtered to enter the engine.  Also, when the oil is cold and very thick, it will tend to bypass the filter through the pressure relief valve because it cannot pass through the element until it thins out somewhat.  If it did not do this, the filter element media would tear open.

A good filter has a strong steel can to withstand the high oil pressure (60-80psi when cold), an anti-drainback valve that actually works without creating too much backpressure, a pressure relief valve that doesn't leak, and a strong paper element and cap that can with stand the pressure and flow of oil without falling apart.  The element media has to be able to trap small particles, but without restricting the flow too much.   Cellulose (paper) media is used on economy filters and works OK.  The fibers in the paper acts as a mesh to block particles down to a certain average size, while allowing the oil to pass through.  Some manufacturers add other media, such as cotton, to the cellulose to improve its performance.  There is synthetic fiber media for the high-end filters that has smaller passages to trap smaller particles, but can pass more fluid through it because it has more of them.  There is also media that is a blend of these two.  There are also "depth" filters that are usually made of synthetic material that has a passage size gradient to it.  In other words, the deeper into the element the oil goes, the smaller the passages get.  This way, large particles are trapped in a different spot than small particles, which allows the filter to hold more particles before it "blocks" (becomes too restrictive).

All filters have to undergo SAE (Society of Automotive Engineers) tests to prove that they meet the engine manufacturer's requirements.  The SAE J806 test uses a single-pass test, checking for contaminant holding capacity,size of contaminant particles trapped, and ability to maintain clean oil.  As an amendment of the J806 test, the multi-pass test also looks for filter life in hours, contaminant capacity in grams, and efficiency based on weight.  The efficiency of the filter is determined only by weight through gravimetric measurement of the filtered test liquid.  Typical numbers for paper filter elements are 85% (single pass) and 80% (multi-pass).  A new test, the SAE J1858, provides both particle counting and gravimetric measurement to measure filter capacity and efficiency.  Actual counts of contaminant particles by size are obtained every 10 minutes, both upstream (before the filter) and downstream (after the filter), for evaluation. From this data filtration ratio and efficiency for each contaminant particle size can be determined as well as dust capacity and pressure loss as a function of time.  Typical numbers for paper element filters are 40% at 10 microns, 60% at 20 microns, 93% at 30 microns, and 97% at 40 microns.

Recommended Filters

Based on the simple criteria above and the information I gathered in the Oil Filter Study, It seems that some filters that are readily available and are of good quality.  I have disassembled many filters and made obervations and measurements on them.  Sadly, some of the most common and popular filters don't cut it in my book.  Those filters are described in the next section.  What follows are filters that I recommend in alphabetical order:

AC Delco Duraguard

This filter does not appear to be AC Delco's original design, but it is still pretty good.  It has one of the highest filter element surface areas with fewer, but very deep pleats.  It also has strong, metal end caps with a nitrile rubber diaphram-type anti-drainback valve and steel bypass valve.  It is one of the better filters you can get for $3.

I have had some feedback about these filters leaking at the seam between the backplate and the can.  Often this was in situations where the engine was modified.  Also, during a recent oil change, I found that this filter did not have the best anti-drainback valve.  It is better than Fram because I have very little valve train noise at startup (I had a lot with Fram).  I now have a NAPA Gold filter on it, which gives me no noise at all.

AC Delco Ultraguard Gold

This filter appears to be a Champion Labs filter.  This is not suprising given that Champion Labs also manufacturers other AC Delco filters for some european vehicles.   Will get the hard data soon...


No real information yet.  I have cut it open and it looks like a very nice filter.   The manufacturer appears to be Baldwin.


No information yet.  One is being delivered.


This is yet another Champion Labs filter that is sold at AutoZone.

Car And Driver

This is a Champion Labs filter that is sold at Target.


This is a Champion Labs filter that is sold at AutoZone.

Fram Tough Guard

Even with all the problems of the other Fram filters, this one is not too bad.  It has a heavier filter element with more surface area, a silicone anti-drainback valve, the cheap pressure relief valve, but with a clever integral screen to keep out large particles, and enough inlet holes for good flow.  The only other drawback to this filter is that it is capped on each end with cardboard instead of metal.  Looking in through the center outlet does not reveal any paper end caps, but they are there.

Hard Driver

This is a one of the few oil filters that uses a synthetic filter element.  It's has a dual-density layering "depth" filter element.  The construction of the filter is what you would expect from a quality filter with steel filter element caps and special epoxy-coated steel mesh retainers to keep the element from flexing.  It also has a good flowing, strong steel case and a zinc-coated backplate to prevent pre-installation corrosion.  I have disassembled but have not measured this filter.   I have not been able to find this filter at any retail stores.

Mobil 1

This filter is made by Champion Labs and uses a synthetic fiber element that can filter out very small particles.  It is rated by the manufacturer at just under the Purolator Pure One as far as filtering capability, but is still very much above conventional paper filters.  It also has a very strong construction to withstand high pressure spikes during start-up.  Given the choice between the Purolator Pure One and the Mobil 1 filters, I would choose the Mobil 1 because of the restriction concerns of the Pure One.  However, as with all Mobil 1 products, expect to pay 2 - 3 times as much for this filter.  I have seen this filter sold at AutoZone and K-mart.

Though I have never had problems, I have received feedback from a few people that these filters may leak at the base.  It seems that the seal between the backplate and can may burst under high pressure (at startup).   These were on Ford engine applications.

Mopar Filters (various)

These filters are Frams, Purolators, or Wixes.  Mopar does not manufacture it's own filters, nor do they require anything special from these manufacturers.  Since they basically paint them a different color, stamp them with a Mopar logo, and double the price, there is no reason to buy them.  Sadly, the Mopar Severe Duty 53020311 filter is actually the worst filter of them all.  It is a Fram Extra Guard.


This was a Purolator hybrid.  It had the Premium Plus case (anti-drainback valve, gasket, etc), but with a Pure One filter element.  This is a cheap way to get a Purolator Pure One.  It is sold at many locations including AutoZone, Pep Boys, etc.


They sell two lines of oil filters: NAPA Silver and NAPA Gold.  They are both made by Dana (Wix) and there is no obvious difference between them.  They may have different elements, but NAPA does not state that this is true.


This is a Purolator Premium Plus that I have seen at Murray's Auto Supplies.


This is a Purolator Premium Plus that I have seen at Pep Boys.  Pep Boys also sells the Purolator Premium Plus brand, which is pretty dumb.

Purolator Premium Plus

The Purolator is a solid design.  It seems to have one of the tougher paper filter element of them all and the bypass valve is built right into the cartridge.  There are no internal sealing problems with this filter at all.  There is an assembly string that is wrapped around the filter element, probably to hold it in place while the glue cures in the end caps.  In the ProLine (one of the Purolator clones), the string was wrapped too tightly and had damaged the filter element.   All the other Purolator-made filters (8 in all) had no trouble, and even the damaged one would probably have been fine.

Purolator Pure One

This is an interesting filter design made by Purolator.  Most of the construction of the Pure One is the same as the Purolator Premium Plus.  The big difference is the filter element itself.  It has a dense paper/fiber filter element that can filter very small particles.  The result of this is cleaner oil exiting the element, but more oil restriction.  Purolator addressed this by adding more filter material (more and deeper pleats).  After seeing one of these filters cut open, I am apprehensive about this filter.  It seems to have so many pleats that it is almost a solid chunk of filter element.  It seems like it would end up restricting the flow, more than anything.  Purolator has plenty of data on the filtration abilities of this filter and I don't doubt it, but they have no flow data.  Even so, I don't see any major problems with this filter.  It also sports a silicone anti-drainback valve and a PTFE treated nitrile rubber gasket.


This is a Champion Labs filter that I have seen at AutoZone and Walmart.


Another quality oil filter similar in design to the Purolator.  It has metal end caps on the filter element, a standard nitrile anti-drainback valve, and a seemingly good flow.  They are manufactured by the Dana corperation.  These appear to have a depth gradient filter element, which uses cotton fibers to progressively trap smaller particles as they get deeper in the filter.  This helps maintain good flow as the filter gets plugged.

Filters To Avoid

The following list of filters have known problems.  You will see well-known names here and will probably be disappointed.  This is because many of these brands have stopped making their own filters and buy from a common manufacturer.

Fram Extra Guard

Years ago Fram was a quality filter manufacturer.  Now their standard filter (the radioactive-orange cans) is one of the worst out there.  It features cardboard end caps for the filter element that are glued in place.  The rubber anti-drainback valve seals against the cardboard and frequently leaks, causing dirty oil to drain back into the pan.  The bypass valves are plastic and are sometimes not molded correctly, which allows them to leak all the time.  The stamped-metal threaded end is weakly constructed and it has smaller and fewer oil inlet holes, which may restrict flow.  I had one of these filters fail in my previous car.  The filter element collapsed and bits of filter and glue were circuilating through my system.  The oil passge to the head became blocked and the head got so hot from oil starvation that it actually melted the vacuum lines connected to it as well as the wires near it.

Fram Double Guard

Another bad filter idea brought to you by your friends at Fram.  The filter itself is a slightly improved design over the Fram Extra Guard, but still uses the same filter element.  It has a silicone anti-drainback valve, a quality pressure releif valve, and enough inlet holes for good flow.  The big problem is that they are trying to cash in on the Slick 50 craze.  They impregnate the filter element with bits of Teflon like that found in Slick 50.  As with Slick 50, Teflon is a solid and does not belong in an engine.  It cannot get into the parts of the engine that oil can and therefore does nothing.  Also, as the filter gets dirty, it ends up filtering the Teflon right out.  Dupont (the manufacturer of Teflon) does not recommend Teflon for use in internal combustion engines.  Please do not waste your money on this filter.


This filter is a Fram!  It is the exact same design as the Fram Extra Guard filter and it is junk.  On the up side, it costs $1 less than the Fram version.

Quaker State

This is another Fram Extra Guard that I have seen at K-mart.  It used to be a Purolator, but Quaker State is now owned/controlled by Penzoil...

Subject: Re: oil filters - pep boys
From: edh@wheeler.unr.edu (Ed Hackett)
Date: Sept 1, 1995
Newsgroups: rec.motorcycles

In article <41vcpe$9e5@twiddle.eng.umd.edu> knee@Glue.umd.edu (Robert S. Fourney) writes:

Why should I give the Honda crooks money and encourage them? If anybody knows if Emgo is any good, I'd appreciate knowing. I've used them before with no noticable problems when inspecting them at removal. They look as solid as the fram and Honda filters. (Note, element type, not screw on, I _can_ see the filter, not just a can). I bought a box of Honda filters (same size fits all my bikes) a while ago and just ran out this year. I"ve been making do with fram's until I get some info on Emgo. Anybody know anything about them?


I know of two BMW engines that were destroyed by Emgo filters. The glue used to hold them together melted under high oil temperatures, the filters fell apart, and the glue then hardend in the oil passages when the bikes cooled. The next time they were started the oil passages were blocked with glue and the engine was destroyed.

If you want to use after market, stay with Fram.

Ed Hackett edh@maxey.dri.edu The Desert Research Institute
DoD #0200 WMTC BMWRA DIOC Reno, Nevada (702) 673-7380
KotLS KotLE DotD #0003 I'm not really a chemist, I'm just one of
BMW K100RS, Moto Morini Camel them motorsickle sonsabitches. __=o&o>__

From: Kalalahti Matti k124476@ee.tut.fi>
Subject: Oil filter test results!
To: toyota-l@cyberspace.cyberauto.com (Toyota mailing list),
toyota-mods@cyberspace.cyberauto.com (Toyota-Mods mailing list),
supras@cyberspace.cyberauto.com (supras),
mr2-interest@cyberspace.cyberauto.com (mr2)
Date: Fri, 7 Jul 1995 00:57:49 +0300 (EET DST)
Sender: owner-toyota-mods@CyberAuto.Com

The Finnish car magazine "Tuulilasi" compared oil filters in its latest
issue. The filters tested were all for Toyota Corolla with A-series engine.

Results in short:

Champion C138       Very good
Clean DO 851          Very good (with size reservations)
Biltema 502077        Good (with size reservations)
Purolator Micronic    Good
Teho OK 174           Good (with reservations)
Fram PH 4967          Satisfactory
Motorcraft EFL391   Satisfactory
Mann W68/80           Passable
M-Filter MH 3347     Passable
Toyota 90915-10001 Inferior
Vic C-110                  Inferior

"Clean" filter was was wider than others, and "Biltema" longer.

What did they test?

1) Filtration

Filters were tested with a test equipment conforming to standard ISO 4572.
The test oil was recirculated through the filter, and dirt was continuously added to it. The test dirt consisted of particles smaller than 200 micrometers. I've picked the figures below from the graphs on the magazine. 15 mg of dirt was added to each liter of oil passed through the system. Oil flow rate was 25 liters per minute.

After 5 minutes, % of each particle size [micrometers] filtered:
40 30 20 10

Champion 98 91 64 19
Clean 99 91 66 16
Biltema 99 91 62 16
Purolator 97 86 60 11
Teho 96 89 61 17
Fram 98 87 55 9
Motorcraft 99 90 61 12
Mann 98 88 56 10
M-Filter 96 85 50 10
Toyota 88 77 31 0
Vic 87 71 39 4

After 10 minutes, % of each particle size [micrometers] filtered:
40 30 20 10

Champion 97 90 63 18
Clean 97 91 62 13
Biltema 95 88 56 11
Purolator 97 82 52 9
Teho 98 86 56 15
Fram 97 85 51 5
Motorcraft 97 92 62 16
Mann 96 83 50 7
M-Filter 94 80 47 9
Toyota 81 60 25 1
Vic 81 68 39 4

time until blocked (bypass valve opens):

Champion 16-18 min
Clean 21-23 min
Biltema 29-33 min
Purolator 22-26 min
Teho 16-18 min
Fram 22-26 min
Motorcraft 13-15 min
Mann 25-27 min
M-Filter 19-27 min
Toyota 16-23 min
Vic 20-20 min

2) Anti-drainback valve operation

All except Vic held the oil.

You can test this yourself, if you want. Find a bolt that fits on the thread in the filter, fill the filter with oil, and with the bolt
screwed in, turn the filter to its side, like it is on the engine block. Does it leak?

3) Bypass valve operation

Some filters leaked slightly through the bypass valve early before the filter elements were blocked, but at worst only 22ml/min.
Compare that to the 25000ml/min total flow in the test, and you see that it is totally insignificant.

Make your own conclusions. Before this I thought Toyota filters would be the best one could get (even though I've used Teho myself
because it's 5 times cheaper). 
Matti Kalalahti | Toyota Carina Coupe GT-T TwinCam Turbo '82
k124476@ee.tut.fi | RWD * IRS * 3T-GTEU * 195+-15hp@4200-6700rpm
A Huge Evergrowing WWW Home Page * http://proffa.cc.tut.fi/~k124476/


From: Neon John <johngdNOSPAM@bellsouth.net>
Subject: Re: RFI - Gulf Coast Filters
Date: Tue, 19 Oct 1999 04:09:48 EDT
Newsgroups: rec.outdoors.rv-travel

Dbaleria wrote:

> Anyone out there using the Gulf Coast Extended Oil Drain filter system  that use a roll of paper towel as the element? It does not replace the factory, rather is in addition to i.) They claim substantial benefits. I have not priced them (not on their web site: www.gulfcoastfilers.com , but they claim they pay for themselves in 30,000 miles, all branches of the military use them, and that they remove particles down to 1 micron. I have not seen any test reports on them. Thanks in advance.

*Sigh* This scam seems to makes its way around every 8-10 years. Guess it's time again.

A few things to think about.

First off, the notion that some guy working in his dingy-lit basement is going to come up with a revolutionary new product that
the "big guys" missed is, while romantic, simply a myth. With a tiny few exceptions, this just ain't gonna happen. Think about it
for a moment. If a roll of toilet paper or paper towels or whatever is such a good but cheap oil filter, why do you suppose that not a
single one of the many filter makers has not just stuck such a roll inside a metal filter can and upped their profits? After all, these
guys spend millions to figure out the cheapest way to make a filter that works.

Get a handful of toilet paper or paper towels. Find a beam of direct sunlight. Scrunch and grind the wad of towels in the beam of
light. Observe all the crap that comes floating out and contemplate how good that might be for your engine.

consider that the pulp used for paper towels is among the cheapest going. Nothing in particular is done to remove grit, abrasives or
other contaminants. A little built-in grit won't hurt your hands or your tushie a bit but think what it will do to your engine.

If you ever get a chance to do so, look at an X-ray of a roll of paper towels. Observe all the flecks of metal and rock in the
paper. Most of this is trash that makes its way into the pulp via the recycling stream.

How small a particle a filter can catch is only part of the issue and not even a very large one at that. Particles below a certain
size have no effect on the engine because they are smaller than the minimum oil film thickness. Far more important is how effectively
the filter traps trash without excessive pressure drop, how much crud it can hold before either blocking or blowing out and its
resistance to blowing out. Another major issue is how the filter handles water. Think of what toilet paper or paper towels do when
they get wet. Moisture gets in the oil from condensation and from running the engine without fully warming the oil.

Truth be known, the oil filter is only a small, albeit important part of engine life. Witness the durability of the VW bug engine
which has no filter at all. Much more important is the operating conditions. Making sure the oil is properly warmed on each trip is
the best thing one can do to extend engine life. The overwhelming proportion of the total wear on an engine occurs in the first few
seconds of operation. When the oil is not allowed to properly warm, it never gets to the proper viscosity and it never loses its water
load. Water + oil + combustion byproducts = acid + sludge. Notice I said nothing about oil change intervals. This 3K mile
change interval that the oil companies and quickchange joints have promoted is THE con of the 90s. Rather than get in a pissing match
with others who will want to argue figures, I'll just describe my practice which is based on significant research using oil analysis
as well as experience. I change the oil and filter in my gas engine vehicles no more often than every 10k miles. My oil analysis data
indicates that this is a conservative number for my driving style. I have no diesel vehicles and so can't comment on that. In my
"fleet", a 75 Datsun 280Z sportscar with 360k miles, a 14 ft Chevy step van with a little over 200k on its small block, a 68 Fury with
about 100k on the clock, a BMW 635CSi with 100k on the clock and a Toyota Camry with 150k on the clock. None burn any oil, though the step van and the Fury do leak from the main seals. I should also note that I buy whatever is the cheapest properly rated oil available. This is usually the Wal-mart house brand, though sometimes Valvoline will have a sale running. I freely mix brands
of oil. Shame on me :-)

What is really interesting is to cut open a 10k mile oil filter and back flush the element to observe what has been caught. An engine
that has been properly warmed most every time leaves almost nothing in the filter. Typically a very few very fine metal particles from
normal wear.


John De Armond
Neon John's Custom Neon
Cleveland, TN
"Bendin' Glass 'n Passin' Gas"


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