Engine Oil Filters Overview
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.
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
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.
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
This is yet another Champion Labs filter
that is sold at AutoZone.
This is a Champion Labs filter that is
sold at Target.
This is a Champion Labs filter that is
sold at AutoZone.
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.
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.
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
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.
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
(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.
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
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.
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.
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.
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.
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: email@example.com (Ed Hackett)
Date: Sept 1, 1995
In article <firstname.lastname@example.org> 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.
From: Kalalahti Matti email@example.com>
The Finnish car magazine "Tuulilasi" compared oil filters in
Results in short:
Champion C138 Very good
"Clean" filter was was wider than others, and
Filters were tested with a test equipment conforming to standard ISO
After 5 minutes, % of each particle size [micrometers] filtered:
Champion 98 91 64 19
After 10 minutes, % of each particle size [micrometers] filtered:
Champion 97 90 63 18
Champion 16-18 min
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
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.
Make your own conclusions. Before this I thought Toyota filters would be
the best one could get (even though I've used Teho myself
> 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
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
consider that the pulp used for paper towels is among the cheapest going.
Nothing in particular is done to remove grit, abrasives or
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
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
Truth be known, the oil filter is only a small, albeit important part of
engine life. Witness the durability of the VW bug engine
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