Smaller Oil Filters Less Efficient?

[helios]

I drive a Subaru(non-turbo). A few years ago Subaru started using a smaller, downsized oil filter instead of their usual full sized filter.
Are the smaller filters less efficient in any way? There appears to be less filter material in the smaller filters.
Think 5k mile replacement intervals is pushing it?

 

[Hokiefyd]

Do you mean less efficient or have less capacity? I believe those are two different things.

They probably have less capacity, but I'm not sure they have a different efficiency.

 

[bullwinkle]

Efficiency increases as the filter pores plug with debris (until it fills up and goes into bypass), but usually a smaller filter has less capacity.

 

[ZeeOSix]

The 4 smallest spin-on filters that Purolator makes are advertised as less efficient than the larger ones, specifically; 99.9% @ 40 microns for the smaller filters vs. 99.9% @ 20 microns for the larger filters.

I don't think Purolator uses different filtering media in these smaller filters, but they do have a different bypass valve design (ie, the "45 record adapter" flat spring with metal-on-metal seal) that may leak some unfiltered oil which might be decreasing the measured efficiency.

The efficiency might also be somewhat dependent on size. Purolator's spec is specific to their large filter 13001. If the same GPM is flowed through a large filter, the fluid speed will decrease and also the PSID, which might have a bearing on the efficiency performance.

 

[helios]

Less oil capacity in the smaller filter? So what? I don't think that there's more than a 5 or 6 ounce difference in capacity between the smaller filter and the larger one.
I'm thinking that there's less efficiency with the smaller filter, but I've read that the smaller filters use a more efficient media material....dunno if it's true.
I'm getting some Mann oil filters; they're full sized and a high quality brand.
I've been using Denso oil filters, still got several of them...they're downsized although Denso is a quality manufacturer. I won't use the Densos any more unless it can be shown to my satisfaction that they're just as efficient as the larger filters.

 

[ZeeOSix]

Originally Posted By: helios
Less oil capacity in the smaller filter? So what? I don't think that there's more than a 5 or 6 ounce difference in capacity between the smaller filter and the larger one.


When he said "capacity", he meant dirt holding capacity of the filter media, not the volume of oil the filter holds.

 

[helios]

Ok then, would it be safe to say that smaller filters normally have less dirt holding capacity and reduced filtering efficiency?
Would some manufacturers, at least, use a more efficient filter media to compensate for smaller size?
Or maybe it would be best to not go for more than 3k miles on a smaller one.

 

[ZeeOSix]

Originally Posted By: helios
Ok then, would it be safe to say that smaller filters normally have less dirt holding capacity and reduced filtering efficiency?


It would be safe to say that smaller filters will have less dirt holding capacity, but not necessarily reduced filtering efficiency. Nobody has really nailed down the correlation (if there is a measurable one) between filter size and efficiency.

Originally Posted By: helios
Would some manufacturers, at least, use a more efficient filter media to compensate for smaller size?
Or maybe it would be best to not go for more than 3k miles on a smaller one.


The smaller the filter, and the more crud an engine produces will determine how short the OCI should be. A super clean engine might be able to go 10K miles on a small filter, whereas an old dirty engine might only be able to go 3K on a large filter.

Cutting open filters for inspection is what will give you a good idea of how long a specific filter can go on a specific engine.

 

[dwendt44]

Most likely the manufacturer has figured out that the new smaller filter still filters well enough and has enough capacity to last through the recommended oil change interval.
Perhaps when they buy filters by the thousands, there's a price break for them with the smaller filter.

 

[Bottom_Feeder]

A smaller filer of the same product line will more than likely use the same media, just less of it to fit in the smaller can. This is an assumption on my part, but Purolator's odd efficiency numbers say otherwise.

Since a smaller filter will hit it's capacity limit sooner, logic would dictate that it shouldn't be put in use as long as a larger filter on the same engine. I certainly wouldn't go more than 5k on one of those shotglass-sized filters, and that's only on a clean, well-maintained engine.

If you have the room, you could try a Purolator 14460, Champ 2869, or one of their clones. They are the old-style larger filters that fit Subarus of my car's generation.

 

[Bottom_Feeder]

Originally Posted By: helios
I'm getting some Mann oil filters; they're full sized and a high quality brand.

They are probably relabeled Purolator Classics, nothing special. Just a heads up.

 

[ZeeOSix]

Originally Posted By: Bottom_Feeder
A smaller filer of the same product line will more than likely use the same media, just less of it to fit in the smaller can. This is an assumption on my part, but Purolator's odd efficiency numbers say otherwise.


My theory is that the 4 smallest spin-on filters from Purolator have worse efficiency because of their metal-to-metal bypass valve design. If the bypass valve leaks even a hair it will hurt the efficiency of the filter. Could be they leak just enough to decrease the measured efficiency some.

 

[Radman]

Originally Posted By: ZeeOSix
The 4 smallest spin-on filters that Purolator makes are advertised as less efficient than the larger ones, specifically; 99.9% @ 40 microns for the smaller filters vs. 99.9% @ 20 microns for the larger filters.

I don't think Purolator uses different filtering media in these smaller filters, but they do have a different bypass valve design (ie, the "45 record adapter" flat spring with metal-on-metal seal) that may leak some unfiltered oil which might be decreasing the measured efficiency.

The efficiency might also be somewhat dependent on size. Purolator's spec is specific to their large filter 13001. If the same GPM is flowed through a large filter, the fluid speed will decrease and also the PSID, which might have a bearing on the efficiency performance.


Zee0Six, you are on to something for sure. When the filter medium is half the area you must double the size of the micron rating to prevent differential pressure from doubling. The larger area filter would afford a tighter micron rating. More area = less dp.

 

[chubbs1]

You would have to go with Fram. Their PH/TG 6607 which is the equivalent to a Purolator P14612, it is what my Altima calls for, very small, and Fram TG is the only filter I can find that has 99% efficiency @ >20 microns in the single pass test. The Extra Guard has 95% @ >20 Microns. They also hold less dirt, it only makes sense. A Very large filter is going to hold more dirt than a very small one.

 

[Bruce T]

Yes, Z06 and Radman discuss everything. It's either the smaller can or the bypass valve that lower the efficiency rating. I agree that companies usually don't switch to a more porous media in their smaller filters.

 

[Texan4Life]

Doesn't oil velocity effect efficiency also? that is how fast the oil is flowing though the media.

 

[ZeeOSix]

Originally Posted By: Texan4Life
Doesn't oil velocity effect efficiency also? that is how fast the oil is flowing though the media.


I would certainly think so, as more GPM flow through a fixed media area means more velocity and also means more delta P (PSID). With more delta pressure across the media, it's more likely that larger particles get forced through the media material.

 

[SteveSRT8]

Yep, no filter can allow a large flow without losing some filtering efficiency.

It's always a trade-off.

 

[Filter guy]

Hmmmmm.

Where to start.

There are a number of variables to take into account. Some of which have been mentioned already.

But one that most don't know about is the thickness of the media. You can get a PH8A size ( large can) and use a thicker media with X number of pleats.

Then you can get a smaller filter for Asian engines , use thinner media and increase the pleat count to compensate.

Efficiencies are dependant on what the filter manufacturer want to do as long as they meet OEM minimum requirements.

Now I have mentioned before that Asian and European engines tend to have less efficient medias in their OEM filters. ( general statement ).US aftermarket filters tend to have an efficiency race as to who has the best filter media. So any US made filter from the good, better, best always tends to have more efficiency than the Asian/European manufactured OEM filter does. ( US manufactured filters for Asian/European OEM tend to have better efficiency than their offshore counterparts).

Medias that are thicker tend to be more cellulose in structure. Even those can achieve the necessary efficiency without much, if any, glass fibers being added.

But the thinner media needs the glass fibers added to achieve similar efficiencies. And dirt holding capacity.

All filter companies use multiple media grades and have access to a lot more for specialty or low volume runs.

 

[river_rat]

Originally Posted By: Texan4Life
Doesn't oil velocity effect efficiency also? that is how fast the oil is flowing though the media.

Yes. Lower face velocity (more media) tends to more particles trapped.