Oil filter analysis

Last Updated on July 22, 2024 by Mutiara

The primary motivation behind this study was to provide information about what oil filter brands are made by which manufacturers. The secondary motivation was to uncover some of the obvious internal construction issues of these manufacturers. This “study” is not a “test”. The SAE J806 and J1858 tests were designed to test the filtration capability of these filters, but unfortunately they have several short comings. These include issues such as anti-drainback valve functionality (valve train noise, etc.), filter element containment capability (how long before it blocks and bypasses–related to surface area), and many testimonials that appear to point in the direction of certain manufacturers.

The primary shortcoming of this study is the small sampling size. For example, only the Ford 5.0 L filer was tested, and later discovered that some brand names use different manufacturers for different applications. Another shortcoming is the lack of testing of the filter element media itself.

It should be obvious that some manufacturers are not being honest about their product. The next time you buy a filter for your car, buy two and hack one open to see what you have. The intent of this article is to provide information and alert the consumer to some little-known issues, not to tell people what to chose.

For this test, every auto parts store in the area was visited and every brand of filter was purchased. The filters chosen were for the Ford 5.0 L V8 engine, due to it’s popularity and the size of the filter. The size allowed any fake miniature internal components to be unveiled.

Disassembly and measurements

Each filter was cut open on a lathe and measurements of their attributes were taken. Simply cutting them open revealed some very interesting (and disturbing) information. The sections below detail each of the filters tested. A summary of the measurements taken can be found in a table for each. 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 for that engine. Here is a description of each table entry:

The construction of the anti-drainback and bypass valves is an important feature. Many are made of nitrile rubber. As long as they have good sealing surfaces, they generally work fine. However, nitrile rubber diaphrams gets stiff in extreme cold and may fail to seal in those conditions. Silicone rubber seals or steel valves are not prone to this. Many bypass valves are spring-loaded steel and work well. Some are spring-loaded plastic and are often not molded well enough to make 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 trap particles. Cellulose media (basically paper) can trap fewer particles and can flow less oil per square inch because there are fewer passages through it. Synthetic media has more passages and can trap more particles and flow more oil than cellulose per square inch. For the same type of media, the smaller the area, the sooner the filter will become plugged and will end up bypassing much of the oil instead of filtering it. Some filters use a cellulose/synthetic blend, so a direct comparison is not possible. More pleats in the element does not necessarily mean more surface area (as you will soon see). In fact, too many pleats can end up restricting the flow too much because there is not enough space between them to allow oil to flow. Most of the cheaper filters use a mix that is mostly cellulose. Some of the better filters use synthetics or synthetic blends.

The shell and backplate thickness are only relevant if your engine’s oil system operates at unusually high pressures. Occasionally a seemingly strong filter can still leak due to a failure at the crimp between the can and backplate. If this happens to you, I would send it back to the manufacturer so that they can solve the problem. Even the cheapest filters have to be strong enough for stock oiling systems, or they will fail SAE tests.

The SAE filtration efficiency and all other data that came from the manufacturers has been removed, since these are often inaccurate numbers.

SAE Tests

All filters have to undergo SAE (Society of Automotive Engineers) tests to 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 much more 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 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).

The SAE J1858 test 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.

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 been removed from the filter sections below.

Oil filters

AC Delco Duraguard PF2

The filter cartridge has a large outside diameter with deep pleats. At first glance, it appears to have little filter element media, but the surface area measure was surprising: 315 sq in. The unit had a solid top end cap because the bypass valve is at the bottom, which is a well constructed spring-loaded steel with a nitrile seal design. The nitrile rubber diaphram-type anti-drainback valve doubles as the seal between the bypass valve and the cartridge. The only drawback to this design is that the bypass valve seats metal-to-metal against the backplate. This could allow oil from the clean side of the filter to seep back into the oil pan, but it wouldn’t allow the dirty oil in the filter to seep back. Oil that is in the main gallery usually leaks out through the main bearings anyway while the engine sits. One disadvantage to the AC 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 past the valve. Even so, I have been getting testimonials that the AC Delco 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 and Purolator filters seal perfectly.

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

Car And Driver SF-1A

This is a Champion filter.

Champ

This filter is manufactured by Champion Laboratories, Inc. (NOT the same guys 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, and STP.

The Champion design has metal end caps on the filter cartridge, with the bypass valve stamped right into the bottom end cap like the Purolator. I refer to this as a one-piece filter cartridge. Though definitely not the same design as the Purolator, it does use the same type of leaf-spring-type spacer 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 of these 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 the oil inlet, one of which is larger than the others. Only the black anti-drainback valve can be seen through the inlet holes. There are 6 large crimps holding the gasket in place. Through the center outlet hole, you can see the bypass valve spring. Usually, the backplate metal is dull, or even rusty.

Deutsch D539

This filter is a Champion filter.

Deutsch D545

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

Fram filters

These filters are manufactured by Allied Signal, Inc.

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

Fram Extra Guard PH8A

This filter cartridge has a small outside diameter with a rather low filter element surface area (193 sqin), and features cardboard end caps that are glued in place. The rubber anti-drainback valve seals the rough metal backplate to the cardboard end cap and easily leaks, causing dirty oil to 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 and are sometimes not molded correctly, which allows them to leak. The backplate has smaller and fewer oil inlet holes, which may restrict flow.

The telltale signs for a Fram Extra Guard are: It has 8 small holes for the oil inlet and a thin, cheap looking backplate, and is currently stamped with a “2Y”. There are 5 very small crimps holding the gasket in place. If you look into the center hole 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 from there). This is the plastic bypass valve.

Fram Tough Guard TG8A

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

The telltale signs for a Fram Tough Guard filter are: It has a better backplate that is usually shiny, with six larger holes for the inlet and 6 spot welds around the them. There are 6 large crimps holding the gasket in place. When you look through the inlet holes, you can see the orange anti-drainback valve. If you look into the center hole 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 from there). This is the plastic bypass valve.

Fram Double Guard DG8A

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

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

The telltale signs for a Fram Tough Guard filter are: It has a better backplate that is usually shiny, with six larger holes for the inlet and 6 spot welds around the them. The backplate should be stamped with 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 looks like it’s made of metal from there).

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 strongest filter available for wide distribution retail sale. It also uses a synthetic media, which inproves filtration and flow. I’m happy to say that this filter is NOT a fake. It is definitely a unique design.

It uses a synthetic fiber element that can filter out very small particles and is very strong. It is rated 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. However, as with all Mobil 1 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 can split.

Motorcraft Long Lasting FL-1A

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

Like the Purolator Pure One, this filter cartridge features a very large element surface area (400 sqin), but with many pleats (64). This packs the filter together rather tightly and may restrict flow somewhat. I could identify the Pure One element media by a purple dye they use at the seam. It also has the mysterious assembly string wrapped around the outside of the element. Like the Purolators, it features a spring-loaded metal 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 cartridge end cap with no gasket of any kind. Some small amount of oil probably leaks through there. It also has the tougher paper filter media of the Wix.

NAPA 51515 Silver

This filter now appears to be a Wix filter. I’m not sure if there is 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 Premium Plus. There were no manufacturing differences, except price.

ProLine PPL-30001

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

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 been compromised. Out of the 8 Purolators (and clones) tested, this was the 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 wrapped around the filter element. I assume that this is there to hold the element in place while the glue in the end caps cures. Of all the Purolator-based filter I tested, there was one (the ProLine) that had filter element damage from this string. Although it was one of five tested, I am weary of this design. Even though the element was crushed a bit, it was not ripped. I will take apart a used one at my next oil change.

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

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

Pure One PL30001

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

The filter cartridge has an even more impressive surface area of 400 sqin. The potential issue is that this filter element is compressed into even more pleats (64) than the Premium Plus. This may restrict flow more than it helps relieve it. It also features a spring-loaded metal 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 manufactures all of the Wix clones. These include NAPA and many OEM filters.

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

The telltale signs for a Wix are: 6 large holes for the oil inlet with only the black anti-drainback valve to be seen through them. There are 6 “notches” that hold the gasket in place. Through the center outlet hole, you can see the bypass valve spring. Usually the backplate metal is shiny.

Wix 51515

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

Conclusions

The purpose of this write up is to provide objective free analysis and hard facts, for conclusions based on these findings see the oil filters article.

Mopar oil filters

This section features a special look at other oil filter alternatives for the 2.2L and 2.5L engines, listed by Mopar part number. Keep in mind that these filters are designed for different engines and have different dimensions. So, it’s not fair to compare them with the other filters on this page. The fact of the matter is, these filters are made by the other manufacturers on this page. My mission was to uncover who is who. What I found is that Mopar uses several different manufacturers.

Conversion Table

If you cannot use the Ford 5.0L filter because of clearance problems, try using one of the alternatives listed here. I have included the outside dimensions so you can see if it will work for you, and they are listed below in order of increasing size. If you find a filter that will fit, you can use that type of vehicle and engine to look up that filter design for other manufacturers (or the same manufacturer, but a different brand).

The chart below shows the part numbers shown here, as well as the engine it belongs to. You can use that information to look up these filters for other brands. I have supplied only the number for those with multiple varieties. Just add the prefix for the model you want. For example, the Purolator 10241 number is the L10241 for the Premium Plus, PL10241 for the Pure One, etc.

Mopar 4105409

This is the stock 2.2L and 2.5L oil filter through about 1990, from the dealership. I have this information here so that you can see why you should not be using this stock sized filter anymore. This one is made by Champion Industries. With a tiny surface area of only 124 sqin it has less than 35% of the surface area of the STP S-01 version (360 sqin), which is also a Champion. Once that small filtration area has been plugged, the oil is directed through the bypass valve and the filter is useless.

Mopar 5281090

This filter is also a stock 2.2L and 2.5L, but for 1991 and later engines, though it fits them all. It is from the dealership and is made by Purolator. It is an upgrade from the stock filter, with about 48% more filtration area. If you have clearance problems with the Ford 5.0L filter because of your alternator, you can try this model. Use the Overall Filter Length and Diameter to see if it will fit.

Mopar 3549957

I purchased this filter from two places, to prove a point. The point is that Mopar filters are like a box of chocolates; you never know what you are going to get. In fact, this seems to be true of many OEM and some clone-brand filters. I purchased one filter from my local dealer and the other from a nearby store that stocks some Mopar parts (Murray’s Auto Parts). Though the Mopar part numbers are the same, the filters are completely different. You can identify the manufacturer of a particular filter by looking at the backplate. See the AC Delco, Champion, Fram, Purolator, and Wix sections for the details on what to look for.

The filter from Murray’s Auto Parts has probably been sitting on the shelf for a little while, so I imagine that it is an older version, but it was not dated. This filter is made by Champion Laboratories. It features the one-piece filter cartridge and some rust on the back plate.

The filter from my local Dodge dealership was dated 02/98. This filter is a Purolator. While the surface area of the filter element is about the same as the Champion version, the Purolator element paper media seems stronger than the Champion Labs paper media. However there is the issue with the assembly string on this version. It’s a catch 22.

Mopar 53020311

This filter was interesting, but unfortunately only in bad ways. I also found this filter at Murray’s Auto Parts, but left it there when I looked at the backplate. I decided to get one from the dealership instead, but it was exactly the same. Cutting it open confirmed it: this filter is a Fram Extra Guard (the radioactive orange one). It’s definitely the cheapest Fram design with the infamous anti-drainback valve sealing against the cardboard cartridge end caps, and the plastic bypass valve. It’s always easy to identify a Fram Extra Guard by the cheap looking, thin backplate with many small holes for the oil inlet. How Chrysler can call this cheap filter a “Severe Duty” filter is beyond me, but it is stamped right on the can. Even Fram makes better filters than this (Tough Guard), but they probably cost too close to the Mopar $6.50 oil filter price for a decent price mark-up. Fram does not list a part number for this filter in the Tough Guard version.

If you really must have this filter, consider looking to another brand, such as Purolator or Wix. Just look up a Dodge Viper or Ram Truck with a 8.0L V10, or use the Mopar Conversion Table above. The problem is that the Purolator is suspiciously like the Fram, however I know it is not a Fram because of the way it was constructed (assembly string, etc). Like the Frams, it has cardboard end caps and a few of the pleats were not glued down. My advise is to avoid all of these filters and go with the Ford 5.0L filters.

Since this filter is popular is Mopar circles, I bought each of these and measured them as well. I was unable to find the AC Delco version anywhere. As you can see, this Fram does have more surface area than the PH8A version, but it is still less than an AC Delco, Purolator, or Wix Ford 5.0L filter. So if you think you are getting a bigger filter with one of these, think again.

Mopar Severe Use 53020311 and Fram PH7226

Purolator Premium Plus L34875

Conclusions about Mopar filters

It should be clear that Mopar filters are really nothing special. Unless you are trying to have a perfect restoration and need that Mopar logo, there is no reason why you should be buying Mopar oil filters. Most of them seem to currently be Purolators or Champions, but that could change at any time.

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

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This writeup and analysis was done by Russell W. Knize.