SAE reports on air cleaner service life and engine wear

[Fillherup]

I just pulled down several SAE reports on air cleaners after reading this forum and learning how important clean air is to engine wear. In the past, my focus had been on oil filters and little regard for air filters. The below facts shocked my base line thinking about air cleaners and my service intervals.

SAE reports key findings:

1) Air cleaners initial efficiency vs final are quite large and depending on initial efficiency could affect engine wear significantly.
2) It is a known fact, from several SAE reports, that engine wear is greater at the initial (5-15%) life of a air cleaner vs the final efficiency.
3) Most high quality air cleaners under normal conditions can go from 30k+ miles to 80K+ miles.
4) Most end users over service their air cleaners and never get the full efficiency and therefore have greater engine wear in the process. Not to mention higher operating cost.

So, after reading this, I wondered were I had gotten the idea that I should change an air cleaner around 7K-8k miles. Since I don't go the max on the oil change, changing the air cleaner more aggressively just seemed to be a 'smart ' thing. I never gave it a thought until now.

Interesting, one of the SAE reports was by Purolator/ArvinMeritor that even tested a filer to 20K+ miles and stated that the service life was within 20-25%. So the filter could go easily to 80-100K miles. But if you look at the Purolator marketing web site they state- 'Purolator recommends replacing your air filer with a new Purolator air filer every 7,500 miles, unless otherwise specified by the manufacturer.'

So now I know why. It does not change the fact that I was over servicing my air cleaner with no benefit and actually increasing my engine wear.

 

[Patman]

I don't like changing my air filters too often because I also believe a new filter is not as good at stopping dirt as a slightly dirty one. But don't go too far, or it'll get worse, as the excess dirt tries to push it's way through.

This is where oil analysis comes in. With a new filter you should see the silicon a bit higher, then on the next intervals it will go down. Once you see it trend upward again, change the air filter again. Oil analysis once again pays off!

 

[jason07-1zzfe]

Most definitely. I have been trying to say this for a while. I plan to test my filter at 30k and I think I will find exactly the same thing...that it could go much longer.

 

[Pablo]

I can almost accept this - BUT - just how bad IS a new paper filter?

This SAE data - are there links?

 

[jason07-1zzfe]

Initial efficiency is pretty low. I have particle analysis efficiency tests of much larger filters for gas turbine intakes.

That is why a clean K&N air filter just plain scares me.

 

[Neil Womack]

I agree we spend to much time worrying about our oil filters. The air filter is more important.

With that said I'm going to try and revive an idea.

Many diesel machines have air restriction indicators that measure in inches of vacuum.

Why do we not use these indicators in all our machines. I know CAT and John Deere sell them. They consist of a small spring loaded plunger in a plastic body with a ratchet mechanism to hold the highs or lowest setting in this case. I think both are connected to the intake with a 1/4 inch pipe threaded fitting.

 

[dickwells]

That's pretty much the way the one in my Chevy truck works. It has a little red plunger that moves to the change position. By the way, maybe there is a market for used air filter elements. Find some of these guys changing every 7500 miles and sell the filters on ebay!

 

[Ryan00TJ]

In my latest oil analysis I installed a new K@N panel filter and this filter was used with the oil interval of 4,630 miles and the silicon count in the UOA was 9 ppm. Very low. That proves to me that a clean K@N will filter pretty good.

 

[Patman]

quote:

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Originally posted by dickwells:
That's pretty much the way the one in my Chevy truck works. It has a little red plunger that moves to the change position. By the way, maybe there is a market for used air filter elements. Find some of these guys changing every 7500 miles and sell the filters on ebay!

---

Or maybe before I put on a new filter, I'll give it to my son to play with in the sandbox for a little while first!

 

[digitaldrifter91]

a long time ago i left an air filter in my car for about 2 years, milage was good so i didnt mind...later the paper got sucked into the throttle body, i felt this when i felt a high power increase and sound as well..turns out that the pressure was so high on the old filter that it collapsed, and my filters for my car has no mesh in the back u kno. good thing my secondary mesh i put in blocked it from getting into the intake manifold and throttle body..

as for this i change my filter at least every year. even if i dont get alot of dirt on it i still change it cause if i sit it on paper it will show that there is alot of oil on it. im not sure abouat the qulity of paper filters but i think that a clean one will at least give me air flow which is what i want plus some filtration u kno...

 

[Americanflag]

If you are going to argue for leaving the filters in a long time you have to give K&N credit, they have been advocating that forever. Maybe K&N is the best...

 

[Malibu]

If a car owner replaced their OEM air filter every 5,000 miles and always used an OEM replacement, would engine life significantly be shortened because they didn't wait until 15-30K to replace the filter? I seriously doubt it. And would Quaker State void its 250,000 mile engine life warranty if owners changed their air filter every 5,000 miles? I seriously doubt that.

Quality car makers instruct owners to change their OEM air filter when "it looks dirty". In my cars the OEM filter looks dirty (full of dust, dirt and bugs) at 10K miles so that's when I replace it.

 

[Fillherup]

Pablo,

Unfortunately the SAE reports are copyrighted and cost $10 a pop. I pulled down three. Of course, the Purolator SAE report shows a dry paper filter had the best efficiency. They only used one type, I assume their filter. On the other hand, the Visteon reports shows worst, average and maximum efficiency for dry paper, treated paper and multi-layer synthetic media. They don't say how large the sample set or who filters they analyzed, but per their findings the dry paper worst case was 91%. The others worst cases were significantly better around 96-98%. Per their reports, the multi-layer was best overall and treaded paper was a close second. Paper filters, per Visteon, range from really bad to pretty good. Maybe Purolator is one of the good guys.

Some SAE papers are basically indirectly product showcases reports. It does not take much reading to figure out the company product in the report. I noticed this initially with SAE oil reports from Mobil. You can always figure out the Mobil oil even when it is just a test #. The filer SAE reports seem to follow the same pattern.

The common data points for all reports was in the initial posting. The agreement on key issues was what really caught my attention.- the initial low efficiency with increased wear and long service life.

If you go by Vistion, paper filters have the most variance. The seems to make sense, since threaded paper and multi-layer cost more and are targeted toward a higher end product. You would hope they are good. Dry paper filters could be all the way from no names white boxes to really good filter.

BTW, I told my 15 year old daughter this last weekend and she suggested that I go the Toyota or Lexus dealer and request pre-owned air filters to preserve my engine.. She thinks I might even be able to develop a business to supply high efficiency pre-owned filters to folks like us.

 

[Fillherup]

Americanflag
Member # 1018 posted February 26, 2003 10:40 PM
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If you are going to argue for leaving the filters in a long time you have to give K&N credit, they have been advocating that forever. Maybe K&N is the best...
[/QUOTE

Any filter will get better until the pressure drop mandates a replacement/cleaning. In K&N case, it is probably an end result of their marketing pitch of long filter service and the hard reality that it really needs to stay in longer to get the E% up, I fear. I am not sure that the overall filtering would be better than a high quality filter with the same dust cake. In other words, the 'dirty' K&N in practice might be equal to a new HQ clean paper filter. But leave the paper filter in for it 'real' service life like you do for the K&N and it might leave the K&N in a trail of dust, so to speak.

 

[dickwells]

This confirms what I see in my 02 truck. At 25K miles the indicator in the air duct has not started to move to the change position. I looked at the filter last week and I could just see an outline of dirt where the air first comes in from the outside.

 

[jason07-1zzfe]

quote:

---

Originally posted by Ryan00TJ:
In my latest oil analysis I installed a new K@N panel filter and this filter was used with the oil interval of 4,630 miles and the silicon count in the UOA was 9 ppm. Very low. That proves to me that a clean K@N will filter pretty good.

---

It proves that for YOU, it may be OK. Proves nothing else. There are other variables. If the airbox is oversized, K&N won't be as much of a detriment. If you drive at low RPM obviously you won't have much velocity at the filter...reducing negative effects. If you were using a high efficieny oil filter, it could have caught the Si that got through. Personally I'd prefer it never to get in there to begin with and have a higher flowing oil filter to let the oil do its job.

9ppm isn't that good anyway. My last analysis was 3ppm @5k miles.

If I had ~$1400 I would get both types tested and end this already. Fact is paper efficiency is low when new, K&N efficiency will be significantly lower and lower for a longer period of time. I'd be surprised if it ever reached the level of paper. Yes on some applications it may be adequate. Personally I am not willing to take that risk.

 

[Pablo]

OK flame shields up 100%:

MUCH MORE DIRT HAS GONE AROUND OR HAS BEEN SUCKED IN AFTER THE FILTER THAN HAS EVER GONE THROUGH OUR AIR FILTERS

but then again I could be wrong...

 

[jason07-1zzfe]

I would disagree if you have installed it correctly and there are no damage to intake boot or anything else wrong that could cause unfiltered air to enter.

 

[Greaser]

I'm with Malibu on this issue...a clean air filter works better than one that has it's pours plugged with fine dust...the whole thing doesn't make any sense to me.I change my air filters every year.I drive in dusty conditions and they look like they need a change when I'm doing it.I take caution to clean my airbox very carefully when I change out.K&N is a drag racing design...to squeeze every last second out of a drag car..they give you an all-together different maintenance procedure if you drive in dusty conditions ,if you go by their website.They recommend a pre-wrap in those conditions...so what does that tell you

 

[Americanflag]

The prewrap tells me nothing... the fact the filter is meant to go 50,000 miles means maybe they are on to something about air filters filtering better after they have some mileage on them.

So far no one has shown evidence it doesn't do the job filtering. Please remember the filter costs 5x what a paper filter costs. I think this allows them to make a better filter.