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Oil filters-would bigger be better?


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It's about oil change time... actually it isn't, but bought the car a little while ago, it's got ~200,000 (98 Legacy Outback) and the previous owner put in the cheapest oil with Fram filter at JiffyLube. So I'd rather put in a decent filter, a pep boys branded purolator, and MaxLife.

 

Was there looking for a filter today, and realized that these filters are just tiny! Would it be better to put in a bigger filter? Anyone know the part number (for any brand) that would fit?

 

[Posted this earlier in a different forum by mistake, so maybe mods can help out with merging the threads... sorry:eek:]

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yeah, i was just looking at filters. the Purulator pure-one PL14460 and the subaru OE filter 15208aa100 is for the 4 cyl whether it is 2.2 or 2.5l. I don't know about bigger being better but if it's bigger then there's just more oil to pump through the filter. I'd just go with what is recommended. were you thinking of putting the H6 filter into your H4?

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Well, I've been researching it online for about an hour, and apparently, OEM is Purolator. http://www.pureoil.com is awesome in that it lists all the parameters, including the pressure of the relief valve. In the recommended filter, it is about twice than for any other filter you can spin of that I found just googling. I guess I'll just stick either with the PL14460 that Purolator recommends or the regular filter under the pep boys brand.

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A larger filter means more filtering media. You'll get less of a pressure drop through the filter at higher rpms, and increased flow which is good for the bearings and whatnot.

K&N filters are generally larger than OE parts, and they also have tighter filtering tolerances. Plus a nifty 1" hex spot welded to the can for easy removal. Although I don't see the point, because if the filter is installed correctly you should be able to loosen it easily with your bare hand.

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bigger will filter better at the same flow rate due to more filter element area.

 

That is simply not true. The level of fitration increases as the filter absorbs larger particulates into it's filtration matrix. The smaller the filter, the quicker it will reach it's minimum fitration particulate size. It's a balanceing act. You want the filter to acheive minimium particulate size quickly and maintain it for the longest amount of time. Too big and you never acheive it at all before the filter is changed - too small and the filter plugs up before being changed. The filter needs to be the RIGHT SIZE for the application and change interval.

 

You people just aren't listening. Read that last paragraph about a dozen times, then go sleep on it, then just step away before you stick your feet in your mouth again.

 

OEM is the RIGHT SIZE. Subaru's engineering division spent plenty of time doing the math. Why does everyone always question the people that build the damn things?

 

GD

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no one has posted the fact that the bigger oil filters at least on the EJ series engine, run the outer part of the filter housing alot closer to the header/exhaust. The closer is gets to the exhaust, the more chance you get to "cook" your oil, especially while at idle and there is no airflow to move that heat from exhaust.

 

In the summer, that heat is even worse, so the smaller the filter, the farther it is away from the exhaust, less chance you cook your oil in there.

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As GD pointed out, it's not about the size, it's about the quality.

 

If you have a big filter, but the media inside is crap (which many Purolator and other brands are), then you've just wasted your money.

 

A smaller, correct filter with good media is better than a larger, incorrect filter with cheap, thin media.

 

Subaru Genuine filters or Napa Gold (made by Wix) are the only ones we will allow on our engines for warranty purposes.

 

Men, it's all about the quality, not the size! ;)

 

Emily

http://www.ccrengines.com

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I was disappointed when Subaru went to the smaller filter size; erroneously I thought that larger was better although I had no data to support that fact.

 

Talking to a number of people whose opinion I respect in regards to engines and their longevity, I came to the conclusion that if Fuji Heavy Industries uses the smaller filter on their larger, more sporty engines (i.e. EJ25, WRX, STi), then the smaller OEM filter is just fine on my '97 model L Impreza.

 

Since I change my oil and filter at a 3000 mile or less interval (let's not get into a discussion on that :horse:) I don't see any point in spending more money, time, and effort into speculative "improvements" regarding oil filters without any hard data to support that.

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OEM is the RIGHT SIZE. Subaru's engineering division spent plenty of time doing the math. Why does everyone always question the people that build the damn things?

 

GD

 

i agree with you that size is not important, quality is. but lets not forget these are the same math people who brought us the 96 - 99 2.5L head gaskets.

 

an intelligent discussion, regardless of the topic, is usually a good thing.

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OEM is the RIGHT SIZE. Subaru's engineering division spent plenty of time doing the math. Why does everyone always question the people that build the damn things?

 

GD

 

Think about this for a minute...

 

Ever modify a Subaru part to make it better? [cricket sounds from afar]

 

Back on topic...

 

Filtration is important on smaller engines. Choosing the correct filter for your application is just as important. Even CCR's requirement is based on opinion. While I do not disagree with it it is just an opinion.

 

Bigger is not always better. The correct application is though.

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That is simply not true. The level of fitration increases as the filter absorbs larger particulates into it's filtration matrix. The smaller the filter, the quicker it will reach it's minimum fitration particulate size. It's a balanceing act. You want the filter to acheive minimium particulate size quickly and maintain it for the longest amount of time. Too big and you never acheive it at all before the filter is changed - too small and the filter plugs up before being changed. The filter needs to be the RIGHT SIZE for the application and change interval.

 

GD

 

 

So is that to say that a filter does not catch any of the smaller particles until after it has filled with the larger ones?

 

Yes filtration does increase due to the gaps in the filter becoming smaller as particulate is captured. But I don't agree that a good quality filter is not designed to work as effectively as possible from day one.

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I only use Wix filters on my Subaru's, mostly because I can't find Mann filters locally.

 

I use Mann on all my euro cars and they seem to be pretty high quality. Wix seems to come close and the local auto parts chain has pretty much every size, including the "big" filters I use.

 

http://www.wixfilters.com/filterlookup/PartDetail.asp?Part=51334

 

That is the stock filter

 

http://www.wixfilters.com/filterlookup/PartDetail.asp?Part=51344

 

That is the one i use if they have it in stock.

 

Either one seems to do the job just fine. Really I would like a second bypass filter but since this is a high mile NA engine worth a couple hundred at best i don't see the point.

 

Remote mounting however would be quite handy. As nice as it is to change the oil without covering the engine in oil its still scary having that filter just hang out down there.

 

 

Edit: Does anyone have any insights into cartridge vs spin-on filters? My BMW uses a cartridge filter in a housing mounted on the front of the engine. Seems like a lot more up front manufacturing cost vs a spin-on fitting and gasket surface.

Edited by coldfusion21
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So is that to say that a filter does not catch any of the smaller particles until after it has filled with the larger ones?

 

Stricktly speaking, no. It's a percentage game. For a given volume of oil passing through the filter, said filter will typically trap X% of small particulates. But that percentage decreases with the size of particulate that is considered (when new), but INCREASES for the same particulate size over the life of the filter. As they age they get better. A smaller filter get's better faster......

 

Understand?

 

GD

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Emprically, the OEM size is good enough that most EJ engines last >200K given reasonable service intervals. "Superior" oil filtration isn't going to help head gaskets, valve guide wear, valve seat wear or prevent the timing belt from cutting loose...all of which are going to determine the lifetime of one of these engines more than any additional oil filtration.

 

Nathan

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In my wife's Ranger, I ran a dual head remote oil filter system. I did that because, at the time, the little truck was seeing abusively hard use. The remote system let me have an additional 3.5-4 quarts of oil in the system over stock setup. That cost me a VERY small bit of oil pressure, but oil and engine temps came down a smidge.

 

At the time, I did some reading on this topic and what I found is that OEM filter sizes seem to be largely based on crank case capacity and intended work load. Filter media does not get addressed in the documentation that I can find, so I suspect that just means the engineers assume a given media (such as Motorcraft/Wix) when setting those specs. As en example, Ford put the 2.3L I-4 into cars as well as the Ranger. It is essentially the same engine regardless of application. However, a NA 2.3 in a Mustang got one filter. The SAME 2.3 in a Ranger got a slightly larger filter and the turbo 2.3 in a Thunderbird got an even larger filter. In my case, that little truck was working so hard all the time that I felt the additional capacity was worth while. It also made oil changes MUCH easier.

 

So, is bigger better? Depends on how you define "better". Is it going to give you better filtration? So long as the media is the same, no. But it will give you extra oil capacity and that means generally lower oil temps and (theoretically) longer oil life.

 

I found that changing the Rangers stock oil filter every 3000, I was getting filthy oil out of it. But I was working it so hard that the oil would start to darken after only 1500 or so. I found that after the change, I could push my oil change intervals a little longer when I had to. I could get 4500-5000 out of it. That little mod more than doubled my crank case capacity. So twice the oil quantity for a 50% increase in oil life.

 

I find that this is "better" for a vehicle that I'm working to death. I just don't work my Subaru's that hard. So OE filters for the Soob's.

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"Superior" oil filtration isn't going to help head gaskets, valve guide wear, valve seat wear or prevent the timing belt from cutting loose...all of which are going to determine the lifetime of one of these engines more than any additional oil filtration.

 

That's true to some extent. Though it's hard to differentiate as the guy that puts on the larger filter probably isn't causeing any major harm in doing so, and at the same time he's maintaining his engine with some care and thought (however misguided). Likely he's checking other fluids, changing them, adjusting things, etc. A well maintained EJ will certainly outlast a poorly maintained one.

 

Very often the engine's internal's do outlast other parts of the car though.

 

GD

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I just installed my last black AA100 filter and was looking to buy some more and found out it's now blue AA12A. has anyone put these side by side? And just read that the internals are by Honeywell (FRAM) and plastic valve?

 

In this picture they look a little longer.

post-20788-136027637554_thumb.jpg

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Every manufacturer of filters has the ability to produce both high end and low end filters. I wouldn't be concerened that the OEM on them is the parent company of Fram. There's many, many products that you could avoid buying because the parent company also owns another unit that makes cheap throw-away stuff. That's business for you. Where there's a demand, there will be a product.

 

GD

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huh? I suspect the backyarder demand has decreased so they decided to reduce the costs of importing the Tokyo Roki and go with a manufacturer (canada) that met specs at a lower price point. I doubt they will be charging less for the cheaper (for SIA) filter eh? Since I can't confirm an aftermarket filter that states 23 psi bpv (using 5w30) I will probably stick with OEM even with cardboard endcaps and silicone anti-drainback (cause it's useless on vertical filters?). ebay case of 12 for 5.17 each-is that good?

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