Best air filter?

I just go to Walmart and get a Fram Air filter and move on.......

HRV oiled OEM:
99.16% initial efficiency
99.57% final efficiency

Aftermarket from a German brand - I'm guessing #'s are similar to fram since they're both non-oiled:
97.15% initial efficiency
98.63% final

Source

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From what I understand reading an article that was posted here in the past, the efficiency makes a difference:

"A previous program of work had revealed that the most damaging particles were in the region of 1-125 microns when measured on the Krumbien Phi scale, a scale commonly used to classify particle size distribution. These particles can pass between piston rings and cylinder walls and eventually become suspended in the engine lubricating oil. Roadside particles have a broad particle distribution of 100 to 1,000 microns. Tests show that air filtration commonly blocks particles greater than 100 microns in size. Consequently, particles smaller than 100 microns were found in the air inlet tract beyond the air filter and can therefore pass into the engine. Samples from the inlet tract and beyond the air filter were examined using optical and electron microscopy. The results indicated the presence of particles considerable smaller than 100 microns, confirming earlier analysis that air filters do not completely prevent the ingress of very small particles."

https://360.lubrizol.com/2020/A-Study-in-Sand

https://360.lubrizol.com/2020/A-Study-in-Sand-Part-2

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This is why I personally prefer OCI's of 5k or less.
From what I understand reading an article that was posted here in the past, the efficiency makes a difference:

"A previous program of work had revealed that the most damaging particles were in the region of 1-125 microns when measured on the Krumbien Phi scale, a scale commonly used to classify particle size distribution. These particles can pass between piston rings and cylinder walls and eventually become suspended in the engine lubricating oil. Roadside particles have a broad particle distribution of 100 to 1,000 microns. Tests show that air filtration commonly blocks particles greater than 100 microns in size. Consequently, particles smaller than 100 microns were found in the air inlet tract beyond the air filter and can therefore pass into the engine. Samples from the inlet tract and beyond the air filter were examined using optical and electron microscopy. The results indicated the presence of particles considerable smaller than 100 microns, confirming earlier analysis that air filters do not completely prevent the ingress of very small particles."

https://360.lubrizol.com/2020/A-Study-in-Sand

https://360.lubrizol.com/2020/A-Study-in-Sand-Part-2

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Best to most of us means best filtering. That being said k&n is just about the worst.
On an iso5011 test k&n stoped between 96 to 97% of dirt. A typical cheap no name paper air filter stops over 99% of dirt.
ACdelco air filters stop greater than 99.9% of dirt.
So to be fair a k&n is probably better than nothing, but I have never seen an iso5011 test ran with nothing.
 
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It's not just some Youtubers showing that K&Ns have poor efficiency, it's also their own published ISO test results.

There's also this independent ISO test, where the K&N passed 45 times as much dust as the most efficient paper filter tested, and 3 times as much as the worst paper filter.

The reason some engines can go hundreds of thousands of miles with poor air filter efficiency is that those vehicles are probably not often driven in really dusty environments. In non-dusty environments, air filtration efficiency hardly matters. In very dusty conditions, abrasive wear becomes the dominant source of wear, and filtration efficiency matters a lot.

Here's a comparison of piston ring and liner wear between two paper filters and a low-efficiency oil bath filter. When dust concentration is low, there's little increase in wear over baseline. In zero-visibility dust conditions, wear is 75 times higher than baseline with the oil bath filter, but less than doubled with the paper filters. Of course, a K&N filter has better efficiency than an oil bath filter, but it would still cause much higher wear in dusty environments than a good paper filter.

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Zero visibility dust conditions? Yep that's me.
 
OEM only (or at least get a paper non oiled) a few months back I was curious just like you, so I decided to buy a TRD oiled filter , which is pretty much a KN filter . After 2 weeks, I took a look and noticed that the filter pleats looked wierd and I did not feel comfortable with running the TRD anymore. It may have been fine and maybe im just a little ocd, but I’ve never had this happen with any oem or paper filter. So I’d stick oem . Here are some pics. 3 pics of before install and 3 pics of 2 weeks after install.

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Honestly it looks better than the OEM. I hate the oil part and use aem dry flow panel or oversized cones but it's structure looks solid. I would keep the TRD and just not wash it unless you find a. refrigerator in there. The more load up the better..
 
YouTube look up project farms air filter tests. Best were wix and Purolator pure one. Worst..a Delco and k and n
Napa golds used too advertise 99.7 % particle stopping. But it's mann and hummel now I think not wix made anymore
 
This is a fairly good test of several air filters for both airflow, as well as filtering ability. I knew the washable K&N's were bad at particle filtration. But I had no idea they were this bad.

 
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This is a fairly good test of several air filters for both airflow, as well as filtering ability. I knew the washable K&N's were bad at particle filtration. But I had no idea they were this bad.


Iso5011 pulls air and dirt through something like an f150 air filter at 100cfm and k&n does pretty well in that test.
Something like a project farm test using flower as test dirt and varying air flow the k&n did exceptionally bad.
 
Because fit is so critical on the engine air filter, I always stick with OEM. I've had a few aftermarket filters over the years that had fitment issues, so now I don't ever veer from OEM. For oil and cabin filters, yes. But not for engine air filters.
I agree as I experienced the same issue on aftermarket air filters for my Hyundai . A UOA pointed out a significant increase in silicon , once I went back to the tighter fitting OEM air filter the high silicon reading went away .
 
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