Best Engine Air Filters. OEM vs Performance
Panel Filter Test
billswebspace.com carried out an in-depth test to find the best engine air filters. This article is a summary of that test.
Short Version
OEM type paper filters filter out more dirt and last longer before becoming a restriction vs “performance” air filters.
The difference in air flow between a stock paper filter and a performance filter is negligible.
And I would say if you get to the point were your stock air filter is a restriction, the problem is the size of the air filter (and the filter box), not the fact that the filter is paper. At least looking at the results of this test.
The Test
Nine air filters for the same Duramax engine were used. The tests were carried out in laboratory conditions to find out which was the best engine air filter.
The engine air filters were compared for airflow when new, for filtration quality and for dust capacity ie how quickly they got blocked.
You see read the full test results here.
Which Filters?
Seven OEM-type paper air filters were compared against two performance air filters.
The OEM paper air filters were from AC Delco, Baldwin, one unbranded filter, WIX, Purolator, Amsoil and UNI.
The performance engine air filters were the AFE Pro Guard 7 and a K&N panel filter.
Air Flow Restriction Results
Which filter flowed the most air when new?
The difference between the best (K&N) and worst (AC Delco) flowing filter, at 350CFM, was only 1.69 inches of water (IN/H20). Convert 1.69 IN/H2O to PSI and we get a tiny 0.06 PSI. (350CFM is equivalent to around 500hp)
At 250bhp/173CFM the K&N restriction was around 0.6 IN/H20, the AC Delco restriction was around 1.6 IN/H20. A difference between the best and the worst filter was only 0.036PSI.
In other words, changing to a performance air filter will probably make no difference to power.
Filtration Quality Results
Which filter let the most dirt through?
–The UNI and K&N filters were the worst performers, letting around 40% more dirt through than the other filters in the test.
7 grams and 7.9 grams respectively.
The best engine air filter was from AC Delco which only allowed only 0.4 grams of dirt through.
The Baldwin filter was second letting 1.1 grams through and in third place was the AFE performance air filter which let 1.8 grams through.
Long Term Performance
Which filter lasted the longest before becoming a restriction?
In general the OEM replacement type engine air filters were less restrictive than the performance filters (after 200grams of dirt had been delivered to the filter). The paper filters flow more air for longer than the performance air filters.
The AC Delco filter was again the best air filter in the test taking 60 minutes before it reached the restriction threshold. This was 27% longer than the second place filter.
The WIX filter came in second place taking 48 minutes before it reached the restriction threshold. However the WIX filter let around 10 times as much dirt through as the AC Delco filter.
Third place was the UNI filter but the UNI filter also let the most dirt through, almost twenty times as much as the AC Delco filter.
Taking into consideration dirt let through and time to blockage the Baldwin filter came in second followed by the unbranded filter.
Best Engine Air Filters – Summary
The AC Delco replacement air filter was by far the superior air filter in this test. It filtered out more dirt, it last the longest before it became blocked and it flowed as much air as the other filters in the test when new. Well, as close as make no difference.
In second place we give it to the Baldwin engine air filter.
Out of the two performance air filters, I think the AFE filter is the one to go for, much better filtration and lasts longer before becoming a restriction vs the K&N filter.
Conclusion – Best Engine Air Filter
From the results on this specific test, the AC Delco standard replacement was the best aftermarket air filter. It was far superior to the performance air filters and standard replacement air filters in all aspects except flow when new but the restriction was very small.
The second place filter was the Baldwin filter. Similar flow, similar filtration but does not last as long as the AC Delco.
Performance Cone/Cold Air Intake Filters – Tested
If you’re interested in the filtration quality and airflow of performance air filters, RevSpeed magazine did a test comparing the big name Japanese manufacturers (& K&N), you can read about it here.
