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Unbiased air filter efficiency -vs restriction testing? #5080986
04/20/19 05:25 PM
04/20/19 05:25 PM
Joined: Dec 2014
Posts: 713
Ed_Flecko Offline OP
Ed_Flecko  Offline OP

Joined: Dec 2014
Posts: 713
Excuse me if this has been discussed before and feel free to point me to the link(s).

We have a ton of ongoing discussion and review about the performance of oil filters. I've only been able to find one review online that looks unbiased that tests a variety of air filters comparing their efficiency -vs restriction, and this study is almost 10 years old:

Is anyone aware of any such tests that are more recent?

Could one contact a given manufacturer and ask them for this type of data, much like we can for oil filters? Do manufactures perform such tests and offer this to consumers?

Thank you,

K-9s teach the suspect that if you'll only be arrested tired.

Support YOUR local law enforcement K-9 Unit!
Re: Unbiased air filter efficiency -vs restriction testing? [Re: Ed_Flecko] #5081112
04/20/19 07:33 PM
04/20/19 07:33 PM
Joined: Dec 2016
Posts: 8,459
Waco, TX
Linctex Offline
Linctex  Offline

Joined: Dec 2016
Posts: 8,459
Waco, TX
This is the only one I can recall:

Posts: 72

On another diesel forum the members banded together to conduct an independent study regarding air filters for the Duramax Diesel. There is a lot of marketing hype surrounding certain aftermarket air filters and we wanted to know if the filters could stand up to their claims. Claims of "superior" filtering ability and dirt holding capacity are among some of these claims. Additionally, many filters are claimed to allow for "better" air flow giving you more horsepower.

This claim of better flow giving more horsepower is a debate all its own, but dyno tests run with a paper filter vs. NO FILTER AT ALL have shown NO INCREASE IN POWER OUTPUT. Therefore a filter with "better flow" will not only give you no increase in performance, it will also let in a lot of dirt while doing it.

The following data is provided by Testand Corp. in Rhode Island. Testand makes the $285,000 machines that perform the SAE J726/ISO 5011 air filter test standard. Any air filter that wants to be tested for performance and efficiency uses this test.

These tests cost $1,700 per filter when done by an independent laboratory.

Testand Corp. was interested in the comparison study and agreed to do the study for us.
Every filter listed was tested in an identical manner according to the SAE/ISO test standard; Here are the results:

In the order of EFFICIENCY (ability to filter dirt) the results are as follows:


AC Delco OE 99.93%
Baldwin paper 99.72%
No name pargain paper 99.32%
AFE Pro Guard 7 panel filter 99.23%
WIX/Napa Gold 99.03%
Purolator paper 98.73%
Amsoil, new style 98.63%
UNI 97.93%
K&N 96.80%

FLOW RESTRICTION from best to worst. Remember, 27.7 inches of water = 1 psi. So, 1 inch of water = .036 psi. The worst (AC Delco) at 6.23 in. water and the best (K&N) at 4.54 in. water is a difference of 1.69 in. of water or a "whopping" .0608 psi. Virtually negligible.

In order from least restrictive to most:

FILTER RESTRICTION in inches of water

K&N 4.54
Mystery bargain 4.78
AFE Pro Guard 4.99
Purolator 5.05
WIX/Napa Gold 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 test dirt it took to create an ADDITIONAL 10 inches of restriction. At that point the test is terminated. This is an indication of HOW LONG a filter is good before it must be cleaned or replaced.

FILTER Dirt Holding Capacity

AC Delco 573.898 grams
WIX/Napa Gold 447.366 g
Purolator 388.659 g
Baldwin 388.154 g
UNI 374.638 g
Mystery bargain 350.402 g
AFE Pro Guard 7 232.516 g
K&N 211.580 g
Amsoil 196.323 g

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 SAE/ISO test.

In order from best to worst, the filters performed as follows:


AC Delco 0.4g
Baldwin 1.1g
AFE Pro Guard 7 1.8g
Mystery bargain 2.4g
Amsoil 2.7g
WIX/Napa Gold 4.4g
Purolator 5.0g
K&N 6.0g
UNI 7.9g

NOTE: During the test the Purolator was reported to have had a seal failure which gave it higher than expected dirt passing.

I hope this data is as eye opening for you as it was for me. SPICER

"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Unbiased air filter efficiency -vs restriction testing? [Re: Linctex] #5081121
04/20/19 07:44 PM
04/20/19 07:44 PM
Joined: Nov 2006
Posts: 21,795
Trav Offline
Trav  Offline

Joined: Nov 2006
Posts: 21,795
Far more important at keeping engine wear especially cylinder bore wear to a minimum than the oil filter IMO. Along with a tight PCV/crankcase vent system and dipstick tube seal will keep most engine damaging particles out.

ASE L1, Master. Deutsch Meisterbrief.
Re: Unbiased air filter efficiency -vs restriction testing? [Re: Ed_Flecko] #5081269
04/20/19 10:34 PM
04/20/19 10:34 PM
Joined: Jun 2017
Posts: 286
New Hampshire USA
Dinoburner Offline
Dinoburner  Offline

Joined: Jun 2017
Posts: 286
New Hampshire USA
Such as this is why I BITOG Thanks

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Re: Unbiased air filter efficiency -vs restriction testing? [Re: Trav] #5081275
04/20/19 10:39 PM
04/20/19 10:39 PM
Joined: Mar 2015
Posts: 6,157
bbhero Offline
bbhero  Offline

Joined: Mar 2015
Posts: 6,157
Originally Posted by Trav
Far more important at keeping engine wear especially cylinder bore wear to a minimum than the oil filter IMO. Along with a tight PCV/crankcase vent system and dipstick tube seal will keep most engine damaging particles out.

I think you are correct Trav... Prevention beats the cure.

I hypothesize that the Asian car manufacturers actually source very high efficiency air filters... For your stated reason. And why they have OEM oil filters that are lower than expected oil filter efficiency.

Nissan Altima 3.5 Coupe
Havoline high mileage 5w30 Microgard 57356
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Re: Unbiased air filter efficiency -vs restriction testing? [Re: Ed_Flecko] #5082933
04/22/19 04:31 PM
04/22/19 04:31 PM
Joined: Dec 2015
Posts: 94
Pocatello, Idaho
compratio10_5 Offline
compratio10_5  Offline

Joined: Dec 2015
Posts: 94
Pocatello, Idaho
This is a good discussion on air filter efficiency and I appreciate those who contributed test results and Trav's real world observations. From SAE paper #970556, Filter Performance Requirements for Engine Air Induction Systems, by Neville Bugli, comes the following quotes: "Engine Air Inlet is the Major Source of Harmful Contaminants" so high quality air filters properly installed and tight induction systems really are critical for optimizing engine life.

"Today, in addition to the overall efficiency, the end user also specifies an initial efficiency requirement for engine intake filters. It has been well demonstrated that clean air filter media exhibits a much lower collection efficiency compared to a loaded filter. Even small amounts of contaminant loading dramatically improves the collection efficiency of the air filter. Engine designers are increasingly concerned about the amount and type of contaminant that could be ingested by the engine."

"Initial efficiency is the key filtration performance measure to determine how well the air filter is protecting the engine. It has been well demonstrated that the initial efficiency of the filter is significantly lower when the filter is new and clean. The efficiency generally builds up after the first 5 - 15% of its useful life. Studies have shown that there is a very strong relation between filter removal efficiency and engine wear. For normal driving conditions it is recommended for engine air filters to have an initial gravimetric efficiency in the range of 98% to adequately protect the engine."

"Generally the overall efficiency is significantly higher than the initial efficiency and is strongly dependent on dust loading characteristics of the media. For both the dry and treated paper media the overall penetration (1- overall efficiency) values dropped by a factor of about 2 or by a factor of 3.3 for synthetic media. The recommended overall efficiency for normal driving conditions is generally 99+% to adequately protect the engine."

Thus we see that filter efficiency is not constant over the life of the filter and to make a valid comparison the testing methods and reporting data must be comparable. For optimal engine life, it is important to not change air filters too early. A filter restriction gauge is the most reliable method of monitoring filter life and these can be retrofitted if you want to optimize engine life.

It's not what you don't know that hurts, it's what you think you know that ain't so. Will Rogers
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