Mostly Mechanical

Auto & Truck Oils, Lubes & Filters – Separating Technology from Hype

How to pick an aftermarket air intake filter that removes dust?

The ads all sound great, but what’s the bare truth?  Most consumers have no idea how to identify and separate marketing smoke-blowers from engineered excellent performance.  So, I’m going to tell you.

Several manufacturers of aftermarket air intake filters make great-sounding claims about how well their engine air intake filters remove the fine, sandy grit that causes engine wear.  It’s good they’re at least making some claims, because most of the worst performers just ignore the issue of wear particles that pass through their filters.  (That’s a consumer hint – don’t buy filters that don’t even attempt to tell you how well they perform.) But how great do those filters really perform in removing dust wear particles? 

One company boasts an ISO 5011 test stand with certified performance that’s “testing to the highest standards”.  Sounds great.  Another uses filter media designed Nanofiber web overlaid on standard cellulose substratewith 5 layers of progressive filtering that’s 99.4% efficient, and “so revolutionary that we applied for and received a patent.”  These filters are probably better than the OEM and OEM-style paper filters.  But what’s the best performance?  As an automotive engineer, I’m adamant in recommending nanofiber filtration technology that’s 98.7% efficient at 2 microns, and 100% efficient at 3 microns.  But 99.4% looks like a better number than 98.7%, right?  So why do I recommend something that appears to be worse performance, and how do I know that nanofiber technology is really better?  Stick with me a couple of minutes to sweep away the fogs of consumer deception, and I’ll explain.

There are four things that count in air filtration:  flow volume, holding capacity, and filtration particle size at a specific efficiency.

  1. Flow Volume.  Some companies focus exclusively on flow volume. 
    Three things to beware:
    – Flow volume at what pressure drop? 
    – What’s your engine’s maximum airflow?  Any flow beyond what your engine can use is useless to you.  In racing or pulling applications with modified vehicles, a high pressure drop (because of high air flow volume) can often collapse the filter.  The engine-damaging results are expensive. 
    – Very low pressure drop at very high flow usually means that at least 50% of meaningful wear particles are passing right through into your engine.
  2. Holding capacity.  How much particulate will the filter hold before the pressure drop across the filter is measureably reducing your fuel economy or power?  In the case of oiled-cotton-gauze filters, how much particulate will the filter hold before it’s passing nearly all the wear particles into your engine?  (The classic answer is “not much”.)
  3. Filtration Particle Size.  The accepted engineering rule of thumb is that damaging wear particles are those with a size of 5 to 25 microns.  Filtering smaller ones is icing on the cake.  Claiming filter performance efficiency on particles larger than 20 microns is a warning sign that the filter performance is very poor.
  4. Filtration Efficiency.  This is listed as a percentage, which refers to what percent of a certain size of particles are captured by the filter.  Beware: in order for either the particle-size or efficiency to have ANY meaning at all, you MUST know both numbers.  Any company who quotes one without the other is simply trying to deceive you, and generally implies that their real performance in removing wear particles is average to poor.

  So that’s the bottom line.  What matters is that AMSOIL’s Ea line of nanofiber air filters is 98.7% efficient at 2 microns.  According to an SAE research paper, that level of filtration reduces particle-based engine wear to levels so low that it is difficult to detect any wear.

What about certified ISO testing?  That’s all legitimately potentially impressive, but “the devil’s in the details”.  What’s the particle size at what efficiency percentage?  They don’t tell you, so you have to figure it out.  That’s pretty tough if you aren’t a trained engineer… and not very convenient for consumers!  For example, an “SAE  Coarse Dust Test” uses A4, and if you look at a typical sample of certified test dust (sent to me by a filter company that advertises their ISO testing), you find that more than 85% of the test dust is larger than 10 microns, less than 35% is smaller than 20 microns in size, and particles that are 5 microns or smaller are less than 10% of the dust. So, “coarse dust” does a poor job in both representing typical driving exposure, AND in representing the 5 to 25 micron wear-particle range that is so critical to your engine.

So what does that mean?  A couple of very important things. 
First, “coarse” test dust is exactly that, and it’s not going to tell you much other than that you have a filter.  It’s a good test of how well your filter will work in a baja race if you’re eating a lot of dust kicked up in front of you.  But is that what you’re doing?  If they really wanted to test and demonstrate meaningful performance, they would use “fine” test dust. 
Secondly, it means that when they do comparison “side by side” “apples to apples” testing against a much better filter, like a nanofiber media, their filter performance can look very good – even identical.  Because as the coarse dust builds up on their coarse filter, the classic “dust cake” forms, enabling the filter to take out much smaller particles than it otherwise could. If they tested it with fine dust, the results would be very different.

AMSOIL doesn’t play games.  Ea filters are tested with fine dust by the most respected certified filtration test lab in the nation, and they publish the particle size and efficiency together with flow and capacity data.  They tell us everything, nothing hidden.  No-one else does that.  15 times the dust holding capacity of oiled gauze filters, at an identical (very low) 0.5 inches of pressure drop.  And just try to beat 98.7% at 2 microns.  Ain’t gonna happen.M1A1 Abrams main battle tank in a cloud of dust

By the way, nanofiber filters don’t use oil, are quickly re-cleanable and re-useable, and are also cheaper to use than any other filter solution.  Yeh.  Use nanofiber and win on time, win on cost, win on performance.  Who can beat that?

The U.S. Army must agree with me, because nanofiber filtration technology is what the M1A1 Abrams battle tank has been using for more than a decade. 

April 4, 2008 Posted by | Amsoil, Diesel, Diesels, Engine Air Filtration, Filtration Technologies, Vehicle Maintenance | , , , | 6 Comments