Clean Air filter lets MORE through?

Status
Not open for further replies.
Joined
Feb 11, 2014
Messages
1,980
Location
Upper Midwest by the Lakes USA
So I was thinking, which my wife wishes I would do less of, and I was thinking.....

Wouldn't a new air filter actually let more junk through? Obviously a dirty one restricts air flow below desired amounts. But for let's say oil analysis, isn't it possible that a brand new air filter could result in oddly higher silica numbers on a used oil analysis?

So. There must be a ' sweet spot' in the life cycle of an air filter?
 
They filter better as they load up and the dust blocks the pores, upto a point where the fitter collapses from vacuum.
The sweet spot depends on the conditions you drive in (desert vs highway)
 
I think its all nonsense. I think cleaner is better. Better airflow better mpg. Dirt restricting more dirt from getting in? Meh..i guess I just dont see a reason to leave in a dirty air filter over changing it. Most filters trap dirt well when new so im not concerned with higher dirt trapping than that. However I also dont believe in changing it out too soon. I typically change it once or twice a year (I drive about 25000kms per year). I like keeping things clean!!
 
According to Purolator, an oil filter is most efficient at the very beginning of the OCI and then right at the end. I am betting an air filter would be the same.

If a UOA has high silicon, they'll tell you to replace the air filer.
 
Interesting subject. I did read where air filters do filter better as a "dust cake" layer forms on top (and a little inside) the media.

A surprising result for oil filters: Paper filter elements especially, tend to erode the fibers slightly, creating larger pore size over usage. Oil filters don't filter as well after a while. If the media has more synthetic fibers, then pore sizes might not increase much if at all.
 
Just changed the air filter on my GM car after 72,000+ miles. Gas mileage did not change but the car started to ingest oil from the pcv system with the old filter. The throttle body had an oily coating on it. This disappeared once the filter was changed. The throttle had to be opened more with the old filter which meant the transmission would downshift too easily. More of the torque is useable with a clean filter. I'll use the new filter for aprox 50,000 miles as the owner's manual suggests.
 
Quote:
According to Purolator, an oil filter is most efficient at the very beginning of the OCI and then right at the end.....

I'm skeptical that Puro information applies across the oil filter spectrum for all manufacturers. That and many knowledgeable long time posters have stated that an oil filter becomes more efficient with use. So imo, that's Puro specific under their stated test procedures.

That aside, air filters do become more efficient with use, even the lead Fram engineer admits that changing too often ( ie. 12k miles/12 month/Fram box) is not best practice. Longer is better as they definitely become more efficient with use.

Below is a classic AF thread by member JOD showing positive results with a long AF fci. Worth reading.

http://www.bobistheoilguy.com/forums/ubb...GRA#Post3167333
 
Originally Posted By: dlundblad
If a UOA has high silicon, they'll tell you to replace the air filer.

I believe they tell you to check your air filter, as it could be improperly installed, damaged, or the seals could be deteriorated and letting in unfiltered air.

I am of the opinion that it is better to run longer rather than shorter, like 50k miles rather than 12k. The Burb has a filter minder, which I am following. The current AF has been in place for about 23k miles and the minder has barely budged. I am guessing I will get 50k+ out of it. I live in a windy and dusty area and am comforted by the fact that the semi-loaded filter is doing a better job of filtering smaller particles than it did when new.
 
Originally Posted By: Rolla07
I think its all nonsense. I think cleaner is better. Better airflow better mpg. Dirt restricting more dirt from getting in? Meh..i guess I just dont see a reason to leave in a dirty air filter over changing it. Most filters trap dirt well when new so im not concerned with higher dirt trapping than that. However I also dont believe in changing it out too soon. I typically change it once or twice a year (I drive about 25000kms per year). I like keeping things clean!!


I'm with Rolla on this one.
 
Originally Posted By: Rolla07
I think its all nonsense. I think cleaner is better. Better airflow better mpg. Dirt restricting more dirt from getting in? Meh.


Yep, it's true...it's called blinding...the tiny holes get partially blocked by dirt and stop more and smaller particles.

How do you figure better fuel economy, with a clean filter when there's a throttle plate choking the engine 99.5% of the time ?
 
And we call it "seasoning".

Potato, potahto, tomato, tomahto!
wink.gif
 
Originally Posted By: Shannow
Originally Posted By: Rolla07
I think its all nonsense. I think cleaner is better. Better airflow better mpg. Dirt restricting more dirt from getting in? Meh.


Yep, it's true...it's called blinding...the tiny holes get partially blocked by dirt and stop more and smaller particles.

How do you figure better fuel economy, with a clean filter when there's a throttle plate choking the engine 99.5% of the time ?


True for any car with a MAF sensor that measures volume. Most of their operation is at part throttle.

Pretty simple actually...
 
The problem is masked today by the use of O2 sensors to control the air fuel mix. As the filter loads up and decreases air flow the O2s will reduce the fuel injected to maintain the closed loop set point.

But they do filter better as the larger openings get clogged up.
 
I just watch my "Filter Minder" If it moves at all, I replace the air filter, I can get about 70,000 to 100,000 miles out of a Donaldson PowerCore on my Duramax.
 
Last edited:
Status
Not open for further replies.
Back
Top