General Oil Filter Info

authored by Russ W. Knize

UPDATE:  Almost 9 years have passed since this project started.  I have finally made some additions and in the process reorganized this article to make the information easier to find.  The biggest change was to move the filter-specific information to a separate page and show the breakdown of the current U.S. filter manufacturers on this page.  I also dated the information as best I could.  My apologies and thanks go to those that sent filters to me all those years ago.  It has taken a lot longer than I ever thought it would, but the information is finally posted.

Description

One weekend in early February of 1999, I set out to every auto parts store in my area and bought every brand of oil filter I could find.  The reference filter that I chose is a common filter used on many Chrysler/Ford engines, which also fits various Jeep, Mazda, and Toyota applications.  The reason is that this is a popular filter used in many applications, it is large so that it will unveil any fake miniature internal components, and it works with the Chrysler 2.2L and 2.5L engines.  Design-wise it is fully compatible with the 2.2L/2.5L oil systems and is an excellent replacement for the tiny "teacup" filter that was originally designed for these engines.  I was able to find over 30 different filters spanning several brand names.  Several smaller studies were done on a few other filter types as well.  Please don't ask for a study for your application, as I can't afford the time or money (mostly the time) to take requests.  Sorry!

• Reference Filter - original, most complete reference for the common Chrysler/Ford filter.

• HP1 Filter - for racing applications of the above engine types.

• Mopar Choices - filters of varying dimensions that are also compatible with the Chrysler 2.2L/2.5L engines

• German Filter - a common filter for German vehicles in order to get a look at some unique brands.

• Toyota Filter - a filter for many L4, V6, and V8 Toyota engines.

Manufacturers

It quickly became obvious that there are only a few actual filter manufacturers selling filters in the USA and the branding is often a ploy to charge more for "premium" brands.  In some cases the manufacturers do seem to be making the filters to different specifications between brands, but in other cases there was no apparent difference at all.  For generic, in-house brands, there is a trend to randomly switch manufacturers over time.

Although all filters have to undergo SAE tests to make it to the market, there is no control over how low the bar is set by a vehicle manufacturer.  There is also the issue of quality control.  Thousands of filters are manufactured at a time and even this small sample size revealed defects.  For something that only costs a few dollars, one is left to wonder how much effort is put into quality control and consistency (watch episode 41 of "How It's Made").  Since premium brands are made at the same plants as cheap brands, is any more effort is spent on quality control on a filter that costs 2-5 times as much?  If the internals are the same (with the possible exception of the filter media), what are you paying for?

The table below lists the filters grouped by their manufacturers.  Click on the manufacturer to be taken to the relevant section of the main article.  Also shown is the exploded view of an example of each manufacturer as well as an image of the backplate for in-store identification.  Click the backplate image for a more detailed view.

Applications

The descriptions and analyses are grouped by filter application for comparison.  The Mopar article actually covers filters for different applications that are also compatible with the 2.2/2.5L engines.  This allows selection of the largest filter possible when filter clearance is an issue.

Disassembly and Measurements

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

The sections below detail each of the filters I tested.  A summary of the measurements I took can be found in a table for each.  I noticed that 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 diaphragms 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 and/or cotton.  Some of the better filters use synthetics or synthetic blends.  There is no way of usefully-identifying the media types by visual inspection.

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.

I have removed SAE filtration efficiency and all other data that came from the manufacturers, since these are often biased towards that particular manufacturer.

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

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.  Usually, the high-end filter manufacturers will display these numbers 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 unbiased.  Therefore all SAE data has been removed.

Warning!

These pages are NOT to be taken as gospel.  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-drain-back 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.  It has been my hope to shed some light in the direction of these issues.  While my perhaps unpopular "two eyes and common sense" approach may not be the most scientific, it is the best I could do considering there was little personal return on the investment of time and money I put into it.

The primary shortcoming of this study is the small sampling size.  Some brand names use different manufacturers for different applications.  Another shortcoming is the lack of testing of the filter element media itself.  Unfortunately I have neither the time nor resources to do this.

I invite anyone with the means to take a larger sampling size and conduct a more complete study, which may include private SAE tests.  I also invite anyone to repeat a study similar to this one on other model filters.  It's really not that difficult.  Just cut them open, take measurements and pictures, and be methodical.

With all of that said, please make your own judgments.  Use this study only as a source of some information that may give you a better idea about which filter brands to steer clear from.  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 cut one open to see what is inside.  My intent was to provide some information and alert you to some little-known issues, not to tell you what to think.

Thank you again Russ for the great information

Reprinted with Russ W. Knize permission

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