Normal for downstream side of air filter to be dirtier?

[paulri]

I just changed the AF in my sienna, at right around 30,500 miles. I noticed after pulling it out, that the side that was facing the path to the engine (downstream) was dirtier than the side that I saw when I pulled the cover off (upstream).

(1) Is this normal?

(2) Does this mean that too much dirt was getting through the filter, and that I should have changed it earlier?

I recently moved to 30K af change intervals, all my manuals say so. Earlier, I would change them (or tried to) around 15K, which is what the af sellers wanted. I'm more than willing to shorten this interval if need be.

The pic on the left was downstream. The pic on the right was dirtier than looks in the picture, but still noticeably cleaner than downstream.

 

[DougR]

Is this an OEM filter? If not, what brand is it?

I have a used air filter that I keep in case I need a spare for a short period of time. The downstream side appears to be about as dirty as the upstream side. When I look at your pictures, I'm wondering if the paper texture is a little bit different on the backside. If so, that may make it appear to be dirtier.

 

[paulri]

No it is not OEM. Honestly I don't recall, and I didn't write it down on my spreadsheet. It would be either Fram or Wix. I don't believe I've bought any other AF, and I know I've bought those two in the past.

 

[4WD]

No it is not OEM. Honestly I don't recall, and I didn't write it down on my spreadsheet. It would be either Fram or Wix. I don't believe I've bought any other AF, and I know I've bought those two in the past.

Think you’d have to know efficiencies … but if it’s low - yeah the real fine stuff makes it through … some are actually bad. I had to pay $25 to get the high efficiency STP for the Tahoe … they have a light coating for the fine stuff …

 

[paulri]

Is that light coating, oil? I've head that this can foul up the maf sensor....

Given all the gunk that I'm seeing on the downstream side, I'm thinking of getting a higher quality filter. I see Fram has an Ultra (what else would it be called?) AIR filter through walmart. I'll look up the STP as well.

Think you’d have to know efficiencies … but if it’s low - yeah the real fine stuff makes it through … some are actually bad. I had to pay $25 to get the high efficiency STP for the Tahoe … they have a light coating for the fine stuff …

 

[4WD]

It’s very light … not drenched like K&N … no issues on the Tahoe or Fusion

https://bobistheoilguy.com/forums/threads/stp-premium-air-filters.260812/

 

[Passport1]

Pretty typical outcome for a filter. Cleaner upstream side, dirtier downstream side just like these when properly used on a healthy, normally aspirated engine;

 

[Snagglefoot]

Where there any forest fires in your area? That ash can be super fine.

 

[paulri]

Nope.

Where there any forest fires in your area? That ash can be super fine.

 

[oldhp]

Are you getting engine blowby back in the intake tube?

 

[Lubener]

Maybe a quick lube guy previously inspected it and reinstalled it backwards. That is if someone does your oil changes for you.

 

[paulri]

Nope. I've been doing them on this car for the past 55K miles, and I put on that air filter. And I don't make mistakes.

Maybe a quick lube guy previously inspected it and reinstalled it backwards. That is if someone does your oil changes for you.

 

[partspro]

Normal, be careful going fancy after market, I've seen filters alter the airflow soo much the mass air flow sensor reported errors

 

[ZeeOSix]

There should have been more and larger sized debris on the intake/dirty side deep down in the pleats regardless of how "dirty" the engine/clean side looks.