Here is the most up-to-date list of filters to be tested. Please let me know if I have any mistakes.
I sent these out today:

1) Used AC Delco OE, 25 k miles from FishHog
2) New AC Delco OE from Bronco
3)Used K&N 17 k miles from Bronco
4) New K$N from SPICER and those sending donations.
5) Used Amsoil, older style, 10k miles from habanero.
6) New Amsoil with recharge oil from Kent Tuttle
7) Used UNI 15 k miles from Eric Merchant.
8) Mystery brand bargain filter (fits our airbox, a lot less pleats, probably for the gasser, looks like a WIX or a Purolator) from flhrciblueice

These are being sent direct to Testand by our members.

9) New Purolator A45314 from flhrciblueice.
10) New Wix (NAPA Gold) from flhrciblueice
11) New Fleetguard from jbplock.
12) New Baldwin from a bear.
13) New and possibly some used UMP / Donaldson conical paper filters from Cliff at UMP.
14) New AFE 54 Series from Tulsa 1718.
15) New AFE Pro Guard 7 from Mark Craig at Diesel Performance Parts, Inc.
16) New UNI with recharge oil from Diesel Power.
17) New Airaid from Diesel Power.

Baldwin Comp Name Comp PartNo Comp Footer Description Remarks
PA4134 ACDELCO A1618C      
PA4134 BIG A 94678      
PA4134 CITGO LAF1520      
PA4134 CARQUEST 88678      
PA4134 FLEETGUARD AF25848      
PA4134 FLEETRITE AFR825848      
PA4134 GENERAL MOTORS CORP. 25332443      
PA4134 KRALINATOR LA1916      
PA4134 LUBER-FINER LAF1520      
PA4134 NAPA GOLD 6678      
PA4134 SERVICE 1 LAF1520      
PA4134 WIX 46678

FINALLY word from Ken. Tests are complete and the data is on its way! I should get a fax in a day or two and the COMPLETE data will be mailed since the programs do not work on E-mail.

Let me first say that Ken is a VERY busy man and stretched himself VERY thin to help out in this project. He also showed a lot of patience with all my annoying calls and E-mails. It is hard when you want to know!!!! Are you done yet? Are you done yet? How 'bout now?

The info Ken had for me on the phone was incomplete and based on memory. He did not have the data in front of him and he did not personally run all of the tests; here is what he could tell me:

One filter sent was unuseable, it had a hole in it. This was sent from Florida and was paper. I will look into this and find out which one it was. The Purolator had a leaky seal but still tested "pretty well".

All filters were tested using PTI Course test dust. Why? It appears that a lot of manufacturers are using course dust instead of fine in their tests in order to BOOST their reported efficiency %. It really does not matter if you use Course or Fine dust as long as all are tested the same. Ken used course so we could compare the results to other claims. With fine dust the ranking based on efficiency would be no different. With fine dust the numbers would be smaller in terms of efficiency %.

In microns, Fine and Course compare like this:

micron size   % in Fine      % in Course

0-2.5          19.7            5.3

0-5             37.3            11.5

5-10           18.2             11.6

10-20          17.7             14.9

20-40          16.6             22.4

40-80          9.9               28.7

80+             .4                  10.9

As you can see a filter will "LOOK" better if using course dust, but side-by-side they will stack up the same.

When I asked about the performance of specific filters he just could not remember it all. He did mention that the Baldwin paper to his best memory was at the top. He also said he does not remember any re-useable filter outperforming paper in efficiency. He also said the foam filters showed dirt on the clean side at the end of the test and may mail them back to me so we can see for our selves. 

No filters were cleaned and re-used. Only the K&N will be cleaned and re-tested. Ken wants to test it using Fine dust to see the difference.

Data coming will be much more than efficiency %. Restriction, etc...will all be in the data. I will likely make a copy of it all and find a way to make a link or get it to jbplock to compile and present.

I am glad to see this coming to fruition and I can rest assured that we did our best. Thanks for the support and looking foreward to the data. NOTE: I am going to be inactive here next week, vacation time. Hopefully I will have some meat and potatoes for you to chew on before then. SPICER

The following filters did NOT make the test. UMP/Donaldson and AirRaid. Cliff at UMP had important issues outside of his control and was unable to get the filters sent to Rhode Island. The AirRaid filter simply never made it and probably was never shipped. None the less, here are the results of the EFFICIENCY test. Flow restriction, dirt holding capacity, etc. will be posted later.

In the order of filtering efficiency the results are:

FILTER         % Efficiency

AC Delco OE             99.93%

Baldwin                      99.72%

No name filter (made for gas engine, 1/3 less pleats)  99.32%

AFE ProGuard 7 (73-10062), panel filter         99.23%

WIX/Napa                 99.03%

Purolator                    98.73%

Amsoil, new style       98.63%

UNI                           97.93%

K&N                         96.80%

Additionally, these 2 were tested using FINE test dust. The K&N was cleaned and retested, the AFE was the conical version:

K&N                        89.85%

AFE Conical             92.33%

Some additional data and info.

Every filter is initially run at 350 cfm and initial RESTRICTION is documented in "inches of water differential pressure". The test is run and dirt is fed at a rate of 9.8 grams per minute. The test is continued until the flow restriction reaches INITIAL RESTRICTION + 10 inches of water. At that point the total dirt fed is documented, total dirt getting past the filter is documented, and with those numbers filtering efficiency is calculated.

A filters ability to "flow air" is indicated by it's "Initial Restriction". A filter's dirt holding/loading capacity is indicated by the " Accumulative Capacity". I will also post the "Accumulative Gain" of each filter which is the amount of dirt that got past the filter during the test.

Read about the difference in Fine vs. Course test dirt in a previous post. Course test dust has the SAME tiny particles as Fine, but the ratio is different. As mentioned before, using Course dust will not change the outcome of filter ranking, only the % number. In other words, K&N will still test worst, but the numbers for all the filters will be smaller. Example: K&N tested with Course was 96.8%, with Fine 89.85%. AFE with Course was 99.23%, with fine 92.33%.

Course dust has ultra-fine 0-5 micron dust in it, just less. Ranking would be no different, just the numbers would look worse. SPICER


FILTER              RESTRICTION in  Inches H2O

K&N                    4.54

Mystery bargain filter          4.78

AFE Pro Guard 7 Panel    4.99

Purolator            5.05

WIX/Napa          5.06

UNI                     5.40

Baldwin              5.71

Amsoil               5.88

AC Delco          6.23

DIRT HOLDING CAPACITY From best to worst. This is the AMOUNT OF DIRT it took to create an ADDITIONAL 10 inches of water restriction. At that point the test is terminated.This indicates HOW LONG a filter is good before it must be cleaned or replaced.

AC Delco             573.898 grams

WIX/Napa           447.366

Purolator              388.659

Baldwin                388.154

UNI                     374.638

Mystery bargain   350.402

AFE Pro Guard 7          232.516

K&N                   211.58

Amsoil                  196.323

TOTAL DIRT PASSING THE FILTER DURING THE TEST. This is how much dirt your engine will take in if you use the filter for the duration that would cause the filter to become "dirty" enough to need replacement or cleaning. The "Dirt Passing The Filter" is the dirt collected by the "Post Filter" during the test.


AC Delco              0.4 g

Baldwin                 1.1g

AFE Pro Guard 7       1.8g

Mystery Bargain          2.4g

Amsoil                   2.7g

WIX/Napa             4.4g

Purolator               5.0g     

K&N                      6.0g

UNI                        7.9g

Note: The Purolator was reported to have a seal malfunction during the test and passed more dirt than it would have with a good seal.                       

Geno and PC - PC and Geno

I don't like to do this openly it isn't my style but I want all the members to know .

I just went through and removed your offensive exchange. I am sick of the constant banter dirtying up a quality informative threads as this one and Also through out this forum chasing one another around with snide remarks. Spicer and others have gone through relentless hours of investigating air filter efficiency.We members don't have to ,don't want to, read through your ridiculous constant banter.

If if it persist not "one" will depart.

End it or I will !


Thanks for the effort. It's looks like the Amsoil guys were right about the gauze -vs- oiled foam but I personally have experienced the poor dirt carrying capacity of the Amsoil filter. The Amsoil filter quickly builds a dirt layer on it's entry surface. Never was enough to trigger the filter minder but it was caked on. I still used it after I noticed how soon it built up but I just cleaned it more often.

I think people looking to cut their ET's go with no air filter at all.... just for the run.

Looks like the best setup full time would be a double AC setup. Double the flow, same cleaning capability.

MAC..... Practice what you preach. I've laid out many decent how-to topics in the Cummins section only to have them bantered. All in fun is OK except now everytime somebody views the how-to they read the banter. Sorry guys... MAC... feel free to unload this statement to keep the topic clean.


Again... best effort I've seen on a real significant subject.