Engine Oil Filter Study

NOTES!!!: I do not take any credit whatsoever for this study. I tried to contact the author, I never received anything back. I am in no way trying to profit from his work, I believe that this is a valuable document, and as such, only seek to preserve it's existence. I have seen this study disappear twice now, I hope to prevent that from happening ever again. Dorian Yeager

UPDATE:  To help reduce some of my email traffic from this page,I have created an FAQ.  Before emailing me with a question, please read theOil Filter Study Frequently Asked Questions first.  I typically don't respond toquestions that are already answered here.

Upcoming Filters

Here are the filters that will be added to this page.  They have already been aquired and disassembled.

- AC Delco Ultraguard Gold PF2
- Amsoil SDF15
- Bosch
- Fram HP1
- Hard Driver HD01
- K&N Gold
- Penske
- Purolator HP1/L390001

Warning!

These pages are NOT to be taken as gospel. The primary motivationbehind this study was to provide information about what oil filter brandsare made by which manufacturers. The secondary motivation was touncover some of the obvious internal construction issues of these manufacturers. This "study" is not a "test". The SAE J806 and J1858 tests were designedto test the filtration capability of these filters, but unfortunately theyhave several short comings. These include issues such as anti-drainbackvalve functionality (valve train noise, etc.), filter element containmentcapability (how long before it blocks and bypasses--related to surfacearea), and many testimonials that appear to point in the direction of certainmanufacturers. It has been my hope to shed some light in the directionof these issues. While my infamous "two eyes and common sense" approachmay not be the most scientific, it is the best I could do considering therewas no personal return on the investment of time and money I put into it.

The primary shortcoming of this study is the small sampling size. I only tested the Ford 5.0L filter. It has come to my attention thatsome brand names use different manufacturers for different applications. Another shortcoming is the lack of testing of the filter element mediaitself. Unfortunately I have neither the time nor resources to dothis.

I invite anyone with the means to take a larger sampling size and conducta more complete study, which may include private SAE tests. I alsoinvite anyone to repeat a study similar to this one on other model filters.

With all of that said, please make your own judgements. Use thisstudy only as a source of some information that may give you a better ideaabout which filter brands to steer clear from. It should be obviousthat some manufacturers are not being honest about their product. The next time you buy a filter for your car, buy two and hack one opento see what you have. My intent was to give you some informationand alert you to some little-known issues, not to tell you what to think.

Description

One weekend I set out to every auto parts store in my area and bought everybrand of oil filter I could find. I chose to get the filter for theearly Ford 5.0L V8 engine. The reason is that this is a popular filter,it is large so that I can unveil any fake miniature internal components,and it fits on most 2.2L and 2.5L engines. Design-wise it is fullycompatible with our oil systems and is an excellent replacement for thepathetic filter that was designed for our engines. I was able tofind 20 different filters spanning several brand names. They are(in alphabetical order):

AC Delco Duraguard PF2
AC Delco Ultraguard Gold PF2
AMSOIL SDF15
Baldwin B2
Bosch ???
Car And Driver SF-1A
Champ
Deutsch D539
Deutsch D545
Fram Extra Guard PH8A
Fram Tough Guard TG8A
Fram Double Guard DG8A
Hard Driver HD01
Mobil 1 M1-301
Motorcraft FL-1A
NAPA Gold 1515
Pennzoil PZ-1
PowerFlo SL30001
ProLine PPL-30001
Purolator Premium Plus L30001
Purolator Premium Plus L390001
Purolator Pure One PL30001
Quaker State Q58A
STP S-01
Wix 51515

I hope to add more brands to this study as I can acquire them. The analysis is sorted by brand name in alphabetical order. In eachbrand section, I have broken the information down into the brand name models,sorted by price. Pictures coming soon!

Disassembly and Measurements

Basically, I cut open each filter on a lathe and took measurements of manyof their attributes. Simply cutting them open revealed some veryinteresting (and disturbing) information.

The sections below detail each of the filters I tested. A summaryof the measurements I took can be found in a table for each. I noticedthat other filter part numbers for the same brand were designed a bit differently. This is probably because of the shape of the can and the requirements forthat engine. Here is a description of each table entry:

The construction of the anti-drainback and bypass valves is an importantfeature. Many are made of nitrile rubber. As long as they havegood sealing surfaces, they generally work fine. However, nitrilerubber diaphrams gets stiff in extreme cold and may fail to seal in thoseconditions. Silicone rubber seals or steel valves are not prone tothis. Many bypass valves are spring-loaded steel and work well. Some are spring-loaded plastic and are often not molded well enough tomake a decent seal, allowing oil to leak passed them.

Probably the most important value here is the element surface area. This helps determine the amount of filter media that is available to trapparticles. Cellulose media (basically paper) can trap fewer particlesand can flow less oil per square inch because there are fewer passagesthrough it. Synthetic media has more passages and can trap more particlesand flow more oil than cellulose per square inch. For the same typeof media, the smaller the area, the sooner the filter will become pluggedand will end up bypassing much of the oil instead of filtering it. Some filters use a cellulose/synthetic blend, so a direct comparison isnot possible. More pleats in the element does not necessarily meanmore surface area (as you will soon see). In fact, too many pleatscan end up restricting the flow too much because there is not enough spacebetween them to allow oil to flow. Most of the cheaper filters usea mix that is mostly cellulose. Some of the better filters use syntheticsor synthetic blends. I'll try to come up with some way of identifyiongthese.

The shell and backplate thickness are only relevant if your engine'soil system operates at unusually high pressures. Occasionally a seeminglystrong filter can still leak due to a failure at the crimp between thecan and backplate. If this happens to you, I would send it back tothe manufacturer so that they can solve the problem. Even the cheapestfilters have to be strong enough for stock oiling systems, or they willfail SAE tests.

I have removed SAE filtration efficiency and all other data that camefrom the manufacturers, since these are often inaccurate numbers.

Other measurements and values are debatable and I will allow you todraw your own conclusions from them.

SAE Tests

All filters have to undergo SAE (Society of Automotive Engineers) teststo verify that they meet the vehicle manufacturer's specifications. There are two tests available for automobile engine oil filters. All filters must be tested with the J806 test, but the new J1858 is muchmore meaningful. Currently the J1858 test is optional. Really,it's a way for high-end filter manufacturers to show off their great filters.

The SAE J806 test uses a single-pass test, checking for contaminantholding capacity, size of contaminant particles trapped, and ability tomaintain clean oil. As an amendment of the J806 test, the multi-passtest also looks for filter life in hours, contaminant capacity in grams,and efficiency based on weight. The efficiency of the filter is determinedonly by weight through gravimetric measurement of the filtered test liquid. Typical numbers for paper filter elements are 85% (single pass) and 80%(multi-pass).

The SAE J1858 test provides both particle counting and gravimetric measurementto measure filter capacity and efficiency. Actual counts of contaminantparticles by size are obtained every 10 minutes, both upstream (beforethe filter) and downstream (after the filter), for evaluation. From thisdata filtration ratio and efficiency for each contaminant particle sizecan be determined as well as dust capacity and pressure loss as a functionof time. Typical numbers for paper element filters are 40% at 10microns, 60% at 20 microns, 93% at 30 microns, and 97% at 40 microns.

NOTICE: Since all of the SAE data I have is from the manufacturers,it cannot be trusted to be truthful. Therefore all SAE data has beenremoved from the filter sections below.

AC Delco

Duraguard PF2

Thefilter cartridge has a large outside diameter with deep pleats. Atfirst glance, it appears to have little filter element media, but the surfacearea measure was surprising: 315 sqin. The unit had a solid top endcap because the bypass valve is at the bottom, which is a well constructedspring-loaded steel with a nitrile seal design. The nitrile rubberdiaphram-type anti-drainback valve doubles as the seal between the bypassvalve and the cartridge. The only drawback to this design is thatthe bypass valve seats metal-to-metal against the backplate. Thiscould allow oil from the clean side of the filter to seep back into theoil pan, but itwouldn't allow the dirty oil in the filter to seepback. Oil that is in the main gallery usually leaks out through themain bearings anyway while the engine sits. One disadvantage to theAC Delco is that the anti-drainback valve seals against a rough backplate. I noticed that if I blow air through the oil outlet, air slowly leaks pastthe valve. Even so, I have been getting testimonials that the ACDelco stops the valve train noise problems associated with the Fram filter,so it may seal fine once it has been exposed to oil. The Wix andPurolator filters seal perfectly.

The telltale signs for an AC Delco filter are: Five large holesfor the oil inlet and 6 spot welds on the rim surrounding them. Thereare no crimps holding the gasket in place. When you look throughthe inlet holes, you can see the metal bypass valve with its 12 small holesand the black anti-drainback valve diaphragm around it. Through thecenter outlet hole, you can see the spring for the bypass valve.

Exploded view:

AMSOIL

SDF15

This filter has been acquired, disassembled, and is awaiting measurements.

Baldwin

B2

This filter has not been acquired.

Bosch

?

This filter has been acquired, disassembled, and is awaiting measurements.

Car And Driver

SF-1A

This filter is a Champion filter.

Champ

?

This filter is manufactured by Champion Laboratories, Inc. (NOT the sameguys who make the spark plugs), and is sold under several other brand names. Champion admits some of these outright, and they are: Lee, Lee Maxi, andSTP.

The Champion design has metal end caps on the filter cartridge, withthe bypass valve stamped right into the bottom end cap like the Purolator. I refer to this as a one-piece filter cartridge. Though definitelynot the same design as the Purolator, it does use the same type of leaf-spring-typespacer at the top of the cartridge and the nitrile anti-drainback valve,which doubles as the cartridge-to-backplate seal, at the bottom. One issue is that I sometimes noticed was some rust on the backplate ofthese filters. Since the rust is usually around by the inlet holes,any loose rust would be caught by the filter.

The telltale signs for a Champion filter are: 6 large holes for theoil inlet, one of which is larger than the others. Only the blackanti-drainback valve can be seen through the inlet holes. There are6 large crimps holding the gasket in place. Through the center outlethole, you can see the bypass valve spring. Usually, the backplatemetal is dull, or even rusty.

Deutsch

D539

This filter is a Champion filter.

D545

This filter has not yet been acquired, but is apparently a heavy-duty versionof the D539 (Champion).

Fram

These filters are manufactured by Allied Signal, Inc. See this emailfroman Allied Signal production engineer.

Fram Extra Guard PH8A

Thisfilter cartridge has a small outside diameter with a rather low filterelement surface area (193 sqin), and features cardboard end caps that areglued in place. The rubber anti-drainback valve seals the rough metalbackplate to the cardboard end cap and easily leaks, causing dirty oilto drain back into the pan. If you have a noisy valve train at startup,this filter is likely the cause. The bypass valves are plastic andare sometimes not molded correctly, which allows them to leak. Thebackplate has smaller and fewer oil inlet holes, which may restrict flow.

The telltale signs for a Fram Extra Guard are: It has 8 small holesfor the oil inlet and a thin, cheap looking backplate, and is currentlystamped with a "2Y". There are 5 very small crimps holding the gasketin place. If you look into the center hole all the way to the topof the filter, you will see a kind of "button" in the end cap of the cartridge(which looks like it's made of metal from there). This is the plasticbypass valve.

Exploded view:

Fram Tough Guard TG8A

This filter has an improved filter element with more surface area (248sqin), a heavy silicone anti-drainback valve with a good sealing surface,the same plastic pressure relief valve but with an integral screen to keepout large particles, and enough inlet holes for good flow. In myopinion, the only real drawback to this filter is that it is capped oneach end with cardboard instead of metal.

The telltale signs for a Fram Tough Guard filter are: It has abetter backplate that is usually shiny, with six larger holes for the inletand 6 spot welds around the them. There are 6 large crimps holdingthe gasket in place. When you look through the inlet holes, you cansee the orange anti-drainback valve. If you look into the centerhole all the way to the top of the filter, you will see a kind of "button"in the end cap of the cartridge (which looks like it's made of metal fromthere). This is the plastic bypass valve.

Far Left: extra guard cartridge. Left: Double Guard. Right:Tough Guard

Fram Double Guard DG8A

This is one of the most expensive filters you can buy. Inside isa basic Fram Extra Guard (PH8A) filter element that has larger diameterholes at the end and has been pre-oiled. You can see this in thepicture above (far left). I assume this is to hold the Teflon particlesin the filter element before the unit is installed. Don't put Teflonin your engine. It does not belong there! DuPont does not recommendusing their Teflon product in internal combustion engines.

Although it has the lowest filter element surface area (193 sqin), itdoes have a clever spring-loaded nitrile rubber anti-drainback valve andbypass valve combination.

The telltale signs for a Fram Tough Guard filter are: It has abetter backplate that is usually shiny, with six larger holes for the inletand 6 spot welds around the them. The backplate should be stampedwith a "1K". There are 6 large crimps holding the gasket in place. The anti-drainback valve diaphragm behind the inlet holes is black. If you look into the center hole all the way to the top of the filter,you will not see the "button" in the end cap of the cartridge (which lookslike it's made of metal from there).

Hard Driver

HD01

This filter has been acquired, disassembled, and is awaiting measurements.

Mobil 1

M1-301

Like the Champ filter, this filter is made by Champion Labs. However,it uses a unique end plate and a thicker can that make it the strongestfilter available for wide distribution retail sale. It also usesa synthetic media, which inproves filtration and flow. I'm happyto say that this filter is NOT a fake. It is definitely a uniquedesign.

It uses a synthetic fiber element that can filter out very small particlesand is very strong. It is rated just under the Purolator Pure Oneas far as filtering capability, but is still very much above conventionalpaper filters. It also has a very strong construction to withstandhigh pressure spikes during start-up. However, as with all Mobil1 products, expect to pay 2 - 3 times as much for this filter.

I have received many reports of these filters failing at high pressures. It seems that the seam where the backplate crimps to the case cansplit.

Exploded view:

Motorcraft

Long Lasting FL-1A

This is an interesting filter. Basically, it is a Purolator PureOne filter cartridge in a Purolator Premium Plus case. Don't be fooledby the differently shaped holes cut into the oil inlet. This is theonly difference. This is a good filter design and if you want toget a Purolator Pure One filter, get this one instead: it is cheaper.

Like the Purolator Pure One, this filter cartridge features a very largeelement surface area (400 sqin), but with many pleats (64). Thispacks the filter together rather tightly and may restrict flow somewhat. I could identify the Pure One element media by a purple dye they use atthe seam. It also has the mysterious assembly string wrapped aroundthe outside of the element. Like the Purolators, it features a spring-loadedmetal bypass valve and a nitrile rubber diaphram-type anti-drainback valve. The bypass valve is stamped right into the bottom end cap of the cartridge,so it is all one piece.

NAPA

1515 Gold

This filter is a Wix filter with the two-piece filter cartridge. As with the Wix filter, the metal bypass valve seats on the metal cartridgeend cap with no gasket of any kind. Some small amount of oil probablyleaks through there. It also has the tougher paper filter media ofthe Wix.

51515 Silver

This filter now appears to be a Wix filter. I'm not sure if thereis any real difference between this filter and the NAPA Gold filter.

Pennzoil

PZ-1

This filter is a Fram Extra Guard (PH8A) in every way, shape, and form. The only difference is the yellow paint and Pennzoil logo.

All the measurements were exactly the same as the Fram Extra Guard PH8A.

PowerFlo

SL30001

As you may suspect by the part number, this filter is a Purolator PremiumPlus. There were no manufacturing differences, but the cost was anaverage of $2 instead of $3.

ProLine

PPL-30001

Yet another Purolator Premium Plus. All measurements were the same. The cost was $2. One thing I noticed with this particular examplewas that the mysterious assembly string was tied too tight and had damagedthe filter element. Although only this one had the problem, I amsuspicious of this filter design as a whole (including all of the Purolators).

<-With String - String Removed ->

As you may be able to tell, the string did not rip into the filter element,it only crushed it. There was no evidence that the element had beencompromised. Out of the 8 Purolators (and clones) tested, this wasthe only one with a problem.

Purolator

Premium Plus L30001

Left to Right: Motorcraft, Purolator Pure One, Purolator Premium Plus

Here is a fairly well designed filter, especially for the price. One odd thing about Purolator's filters is a string that is always wrappedaround the filter element. I assume that this is there to hold theelement in place while the glue in the end caps cures. Of all thePurolator-based filter I tested, there was one (the ProLine) that had filterelement damage from this string. Although it was one of five tested,I am weary of this design. Even though the element was crushed abit, it was not ripped. I will take apart a used one at my next oilchange.

The filter cartridge has an impressive surface area of 316 sqin, whichis very close to the AC Delco Duraguard. The difference is that Purolator'sfilter element is compressed into more pleats (51) than the AC Delco. This may restrict flow somewhat, but not as much in this model than thePure One. It features a spring-loaded metal bypass valve and a nitrilerubber diaphram-type anti-drainback valve, which doubles as the seal betweenthe backplate and the cartridge. Like the Champion, this bypass valveis stamped right into the bottom end cap of the cartridge, so it is allone piece.

The telltale sign for a Purolator filter are: 8 medium-sized holes forthe oil inlet and nothing but a black (or orange for the Pure One) diaphragmto be seen through them. There are 6 large crimps holding the gasketin place. Through the center outlet hole, you can see the springfor the bypass valve.

Exploded view:

Pure One PL30001

This filter has a few improvements over the Premium Plus. It hasa denser synthetic filter media to filter out smaller particles and moresurface area to make up for the flow restriction. Aside from thosethe cartridge is the same construction as the Premium Plus.

The filter cartridge has an even more impressive surface area of 400sqin. The potential issue is that this filter element is compressedinto even more pleats (64) than the Premium Plus. This may restrictflow more than it helps relieve it. It also features a spring-loadedmetal bypass valve and a silicone rubber diaphram-type anti-drainback valve,which doubles as the seal between the backplate and the cartridge. The bypass valve is located at the base of the cartridge, not at the top.

Quaker State

QS8A

This filter has changed from being a Purolator to a Fram Extra Gaurd. This may have been a result of Pennzoil aquiring Quaker State brand name.

STP

S-01

This filter is the Champion Industries filter.

Wix

These filters are manufactured by the Dana corporation, who also manufacturesall of the Wix clones. These include NAPA and many OEM filters.

This filter has metal cartridge end caps, but has a separate bypassvalve that rests against the bottom end cap, like the AC Delco. Irefer to this as a two-piece filter cartridge. Like the Champion,it uses an anti-drainback valve that doubles as the bypass valve-to-backplateseal. Instead of the leaf-spring-type spacer that most filters use,these use a stiff coil spring at the top of the cartridge. Like thePurolator, the filter element paper media is stronger than the Championmedia. The only drawback to this design is that the bypass valveseats metal-to-metal against the bottom cartridge end plate. Thiscould allow dirty oil to seep from the dirty side to the clean side ofthe filter, bypassing the element. The design will not allow oilto seep back into the pan, though.

The telltale signs for a Wix are: 6 large holes for the oil inlet withonly the black anti-drainback valve to be seen through them. Thereare 6 "notches" that hold the gasket in place. Through the centeroutlet hole, you can see the bypass valve spring. Usually the backplatemetal is shiny.

51515

This filter features a good surface area, but a lot of shallower pleats. This makes it similar to the Purolator's pleats.

Conclusions

See the AC Delco, Champion,Fram,Purolator,and Wix sections for information on how to identifythese manufacturers by looking at the backplate. The tell-tale signsare always there.