Oil filters-would bigger be better?

[Markus56]

OR

 

-this is directed at everyone-

 

Instead of arguing over something like oil filter size, micron, re-usable blah blah blah blah, just go to your local NAPA and get the filter recommended for the car you have, I'm sure Subaru had knew what they were doing when they designed your car.

 

<-this sums up this whole thread

 

and re-using disposable filters has to be one of the dumbest things i have ever heard.

[GeneralDisorder]

The thicker the oil, the colder it is, and the smaller the filter, the greater the chances this will happen. In cold climates it's best to use the largest filter available.

 

How do you figure this? The bypass valves are set at a specific pressure. The size of the filter isn't going to change the amount of pressure the pump puts out to any great degree - it shouldn't if designed properly and the engine is operated within it's allowable ambient temp range.

 

GD

[Ginger48]

How do you figure this? The bypass valves are set at a specific pressure. The size of the filter isn't going to change the amount of pressure the pump puts out to any great degree - it shouldn't if designed properly and the engine is operated within it's allowable ambient temp range.

 

GD

 

It's very simple. The less filtering media there is (and Subaru oem oil filters ARE small) and the more contaminants there are in the filter WHEN the oil is cold and thick, the oil IS going to find the least restrictive place to flow through.....and that's the bypass valve. Why do you think oil filter manufacturers install bypass valves in their filters? If they didn't, you'd blow a hole in the filter media. When the bypass valve opens, guess where all the contaminants that were previously trapped in the filter goes? The oil filter manufacturers aren't going to install something that isn't necessary and doesn't ever get used.

 

Conversely, the larger the filter (more filter media) the less restrictive it is and less likely the bypass valve will need to open when the oil is cold and thick.

 

If you use synthetic oil, or you change your oil and filter every 3,000 miles this is most likely a moot point.

 

EDIT:

Oil filter bypass valves are NOT designed to open at a specific oil pressure. They are designed to open at a specific pressure differential. The more contaminants there are in the filter and or the colder the oil is, the greater the pressure differential.

Edited December 13, 2009 by Ginger48
Edit

[Frank B]

General Filter Facts - Oil Filters

 

Since 1954 when we patented the first spin-on oil filter, WIX Filters has been at the forefront of oil filter technology and performance for passenger cars, light trucks, heavy trucks and buses, and off-highway vehicles. SAE J806 tests prove that WIX oil filters hold 45% more dirt than the leading national brand - meaning we keep filtering long after the competition has completely quit. Use our Filter Look-up feature or consult you nearest WIX distributor using our Where To Buy to find the best WIX oil filter for your needs.What the Oil Filter Does...You may take your oil filter for granted, but this small, inexpensive part of your vehicle's lubrication system plays a vital role in protecting the engine from premature wear. Each moving part in the engine and the cylinder walls requires clean oil for proper lubrication and lasting life. The oil filter cleans the oil as it passes through the filter element or filtering media. This prevents abrasive contaminants in the engine lubrication system from damaging engine parts.

 

The better you understand your engine's lubrication system, the more you'll appreciate the vital role your oil filter plays. When the engine is running, oil enters the oil pump through a screened intake. The screened intake -- or oil pick-up -- is located in the crankcase near the bottom surface of the oil pan. The oil is drawn through the screen intake and forced by the oil pump through the oil filter.

 

Oil from the main gallery is also fed through vertical passages to the crankshaft main bearings and through the crankshaft to the rod bearings. Oil thrown from the crankshaft, or sprayed from the connecting rods, lubricates the pistons and cylinder walls.

 

In a typical full-flow type oil filter, the oil flows into an inlet passage and then through the filtering element. After flowing through the filter element, the filtered or "clean" oil passes directly to the main oil gallery. In a partial-flow type filter, the oil returns directly to the oil pan.

 

Oil from the main gallery lubricates the camshaft and the camshaft bearings (and feeds hydraulic valve lifters if used in the engine). On non-overhead cam engines, oil is metered through the valve lifter to a hollow push rod that carries oil for the lubrication of the push rod pivot point, rocker arm pivots and valve guide. Oil Filter MediaThe media is the filtering material in the oil filter element. It essentially determines the efficiency, performance and useful life of the oil filter.

 

There are two basic types of filter media: the "paper" media and the "depth" type media. The primary features of the filter elements are:

 

Particle size retention (filtration efficiency)

Particle size retention is the measure of the degree to which the filter can retain particles of various sizes. Wix has developed optimum particle size retention quality in filter media by extensive engine wear tests including exhaustive testing of filters used in racing, and sophisticated laboratory tests. Wix media in the automotive full-flow oil filter is able to trap and hold essentially all the contaminant particles larger than 25 microns. (A human hair measures approximately 70 microns in diameter. An object that is 1 micron in size is .000039 inches in diameter.) Our filters also capture a high percentage of even smaller particles.

 

Dirt-holding capacity

Dirt-holding capacity is the amount of contaminant that can be removed and held by the filter until the filter ceases to function. The capacity of Wix filters is significantly larger than the minimum requirements to efficiently filter all the oil during the oil and filter change periods as specified by vehicle manufacturers.

 

Resistance to oil flow

WIX full-flow oil filters for automotive applications use arch-pleated, prescription-blended media. When new, the media with a maximized number of pleats has less than 2 psi pressure drop when filtering oil at a rate of 4 g.p.m. at normal operating temperature. This low initial restriction to oil flow protects the vital engine parts more effectively. Parts of an Oil FilterGasket - provides exterior seal between the filter and engine at the engine mounting surface. Mounting Plate - prevents deflection (movement) at the gasket sealing surface. Heavy gage steel plate provides for threaded attachment to the engine. Inner Element Support - provides inner element stabilization and a positive seal between the inner element and the mounting plate to prevent the bypass of unfiltered oil. Upper End Cap - retains element end sealant and filter media, provides an outlet for clean oil, and provides structural rigidity to the pleated media. Lower End Cap - retains element end sealant and filter media. Arch-pleated, Prescription-blended Filter Media - provides a more than adequate filter area. The element has a controlled porosity blended media to assure complete filtration of the oil. Spiral-wound Center Tube - provides internal element support. The spiral design greatly reduces initial flow restriction when compared to other designs. Coiled Spring - ensures a constant load on the inner element to maintain the seal between the upper element end cap, the inner element support, and the mounting plate even during pressure surge situations. Filter Canister - encloses the assembly with a mechanically-locked double seam. The canister provides "flutes" at the closed end for ease of removal with an oil filter wrench.Silicone Anti-Drainback Valve - Stays flexible in extreme temperatures, improves oil flow and keeps oil in filter to prevent engine destroying dry starts. Also provides lasting protection to meet new vehicle manufacturers longer recommended oil change schedules. Nitrile valves can harden and become ineffective over time.

Some WIX full-flow filters include anti-drainback and/or filter by-pass valves. These types of filters are identical to full-flow filters, except that a by-pass valve replaces the inner element support and an anti-drainback valve has been added. The Anti-Drainback Valve prevents oil from draining out of the filter inlet holes when the engine is shut off. It also provides seal between clean and dirty oil at the upper end cap. This is necessary in applications where the oil filter is mounted in a horizontal or inverted position.

 

The Filter By-Pass Valve

If a WIX full-flow filter becomes "clogged", or excessively restrictive to oil flow, the filter by-pass valve ensures continued engine lubrication by allowing the oil to by-pass the filter. Some vehicle manufacturers have the by-pass valve built into the oil filter mounting unit (located on the engine).

 

Other vehicle manufacturers require full-flow filters have the by-pass valve built into the filter itself. All Wix oil filter types recommended for these particular applications include the by-pass valve assembly in the filter.

 

By-pass Valve Assembly -- spring loaded valve assembly that allows oil to by-pass the element under high-differential pressure conditions such as cold oil and/or excessively contaminated media. This allows lubrication of the engine, but without full-flow filtration.

[GeneralDisorder]

The more contaminants there are in the filter and or the colder the oil is, the greater the pressure differential.

 

What you are talking about is a boundery condition. Specifically, the point at which the filter is too dirty for cold oil to flow through it and thus the bypass valve opens. While I conceed that this point can be and surely is being reached by some people's filters, you cannot say when or if this is going to happen before the filter get's changed. That's speculation at best. I would err on the side of saying that Subaru did enough homework to avoid that in normal circumstances (filter being changed on the schedule, and the engine not being a total dirty mess inside).

 

Further - the only reason the larger filter would perform better in your scenario is that it has a larger element - so it's a trade off. As I noted before the element gets better as it ages - you are trading that aged property for a chance to avoid the bypass valve opening when cold - which you can't demostrate even occurs (though under the right circumstance it could). I guess that's a judgment call that would come down to how dirty I thought the engine was inside. I would definitely have to be cutting open every filter to make that call.

 

And at any rate, I'm certain this doesn't happen enough to justify the change in filter size on an otherwise clean engine (and on a dirty one, it should be flushed with ATF and the filter changed more often IMO). And as you pointed out - if you run synthetic's it's likely MUCH less of an issue.

 

GD

[Petersubaru]

It's very simple. The less filtering media there is (and Subaru oem oil filters ARE small) and the more contaminants there are in the filter WHEN the oil is cold and thick, the oil IS going to find the least restrictive place to flow through.....and that's the bypass valve. Why do you think oil filter manufacturers install bypass valves in their filters? If they didn't, you'd blow a hole in the filter media. When the bypass valve opens, guess where all the contaminants that were previously trapped in the filter goes? The oil filter manufacturers aren't going to install something that isn't necessary and doesn't ever get used.

 

Conversely, the larger the filter (more filter media) the less restrictive it is and less likely the bypass valve will need to open when the oil is cold and thick.

 

If you use synthetic oil, or you change your oil and filter every 3,000 miles this is most likely a moot point.

 

EDIT:

Oil filter bypass valves are NOT designed to open at a specific oil pressure. They are designed to open at a specific pressure differential. The more contaminants there are in the filter and or the colder the oil is, the greater the pressure differential.

..I have a hard time understanding how a smaller filter is going to have more dirt in it, since that smaller filter was originally designed or re-designed for its application..newer cars simply do not pollute the oil as cars of yester-yr...my'01 OB is not a carbed model car so bigger is not better so long as I stay within the manuf. specs ...even "Blackstone" has repeatedly said the filter I am useing ( a very small nippon "gray", H2.5"xOD2.75") useing dino oil is doing its job better then the averages he uses..even with extended drain intervals (but not beyond the manuf. recomm.)..generally speaking with the correct 5/30 or thinner even when it is cold and thick, the oil is still designed to go thru the filter media and Not use the by-pass unless someone has strayed far off the rec. specs

[Qman]

As I said before...

 

the only reason for going to a larger filter on a Subaru(that is what we are referencing after all) is for more capacity. It will still catch the same size particulates. It will only filter it's own capacity at any given time.

 

If a WIX full-flow filter becomes "clogged", or excessively restrictive to oil flow, the filter by-pass valve ensures continued engine lubrication by allowing the oil to by-pass the filter.

 

And there you have it. The reason for by-pass. It is designed that way to save the engine. Not for filtration! And the most you'll get to fit a Subaru application would be another half quart any way. A rather mute point in the big scheme of things. If you want to carry a larger capacity than switch out to a WRX oil pan. It will give you a full 5qt capacity.

 

Now, we can go back to modifying those well-built parts!!

[Loyale 2.7 Turbo]

I don't want to Argue your Reasons but Please let me Explain Something that I have Learned by my Own Experience with Many Cars, not only Subarus:

After Some Days without Starting the Engine or even the Every day First Start, due to the fact that all the Oil went to the Oil Pan; when you First Start the Engine, it Takes More Time Without Enough Oil Pressure when the Car Runs on Smaller Filter and Less Time when the Same Car Runs on Larger Filter.

It is Due to the Oil Filter's Own Capacity: the Larger Filter Holds more Oil inside its Own than the Smaller one, also it is Right at the Oil Pump, So the Filter's Oil Helps to Prevent the Engine from Runnin' Without enough Oil when Started: It Supplies the Oil While the Pump gets it from the Oil Pan; So That is Why a Bigger Filter is Better than a Smaller One; but that is the Only Noticeable Difference Between Smaller and Larger Filters...

The Real Reason of Many Sizes in Oil Filters is Just the Available Space on Engine's Bay, not the Performance itself; just like the Real Reason Behind the V Engine Design: is Easier to Fit in a Short Space a V8 than an in-Line 8 engine, isn't it?

I Kindly Suggest you to Try this: if your Subie can Hold Both Sizes of filters and it has the Oil Pressure Gauge, Check how Long takes to Raise it Up when First Start the Engine in Early Morning with the Large Filter and after the next oil Change, check the Same but with the Smaller Filter... without Oil Pressure Gauge: Just Listen to the Hydro Lifters and how long takes the Oil Pressure to Quiet 'em with Both Sizes of Filters and the Same SAE Number Oil.

in Example, my EA82 Wagon can Hold the Purolator L10028 Small Oil Filter and the Purolator L20064 Large Oil Filter, both work just Fine but with the Larger Filter the Oil Pressure Gauge Raises Up Faster after Start than with the Smaller One... Using the Same 20W~50 Oil, and Hydro Lifters Quiet Faster too.

I Hope this can Help.

Kind Regards.

[2.5GL]

http://minimopar.knizefamily.net/oilfilterstudy.html

 

I got this link from a friend some years ago. While not specific to Subaru, It shines some light on the quality of filters available these days. It was last updated in 2008. Site gives insight on materials used in construction of filter media, types of bypass valves, etc, etc. An interesting read for any technophiles out there, and rather relevant to where this thread seems headed...

 

I would suggest starting with one of the two links in the first sentence of the site.

 

L

Edited December 14, 2009 by 2.5GL
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[Ricearu]

NEVER blow compressed air through ANY filter (air, oil, etc), not even a K&N. It makes "holes" in the filter media where larger particles can get through. Defeats the purpose of a filter.