Recently my goto filter has been Purolator PureOne, I had bought them in quantity for my other cars, but since I didn't have any for the OB I had to go to the local auto parts store. The first one I used was a Fram Tough Gard or Ultra Synthetic, can't remember for sure, but the next time and ever since I have used a Wix at the suggestion of the dude at the store who has been there as long as I can remember. He said it had a valve to prevent the reverse flow of oil which would be important for the upside down mount of the filter. OK, as good a reason as any I suppose. So what do the OB Brain Trust say? Which filters are good for the OB and why?
The magical/mystical 23.2psi oil filter bypass spec.
Lord Osis
41 - 60 of 107 Posts
Rub said: Look for my UOAs on the forum. All with the Ultra and all very good to "perfect" according to Blackstone.
Most interesting thing to me from looking at your UOAs is the copper drop-off. The idea of being "finally broken in" at 30k is a kick to consider.
Most interesting thing to me from looking at your UOAs is the copper drop-off. The idea of being "finally broken in" at 30k is a kick to consider.
I've considered that the Subaru OEM filter is a Fram Extra Guard filter and that the Tough Guard and Ultra series filters not only provide better flow but also better filtration over a longer period of time. So if Subaru's flow spec is met at the Extra Guard level it stands to reason that it would be exceeded in higher level filters.
Its really amazing to see some of the reports over at BITOG on these filters. Many people are getting 10 to 15 thousand miles on the Tough Guard filter with no problems, some have stretched them out to 20,000 miles. The Ultra Guard is seeing 20 to 30 thousand miles from many and some are wanting to push beyond 30,000 miles. That is nuts but unless they are all lying on their UOA/UFA reports I consider it quite impressive. I previously thought that no filter could outlast high grade oils but perhaps the tide has turned with the advancement of filtration.
Motorking on BITOG was Jay who worked for Fram as their Technical Resource director and quite often posted there. No longer bc Fram was aquired and he and the staff were laid off in favor of the new owner's staff. He is under a non-compete and also can't talk about them for a number of months.
Before all of that, he said that their 20k filter life was actually tested and worked well out to 30k but corporate counsel had them dial it back to 20k.
Engines produce about 1 gram of cooties per 1k miles and their larger cans hold beyond 30 grams while still giving the high filtering ability and excellent flow.
Bypass Pressure
I know this is an old thread but for some reason, it popped up on my phone's news feed just yesterday. I'm sure someone will give me crap for reviving a year plus old thread.
After working in an industrial setting for a number of years, some of my experience has dealt with filtration; I'm willing to take a really **** good stab at your question regarding why Subaru chose the 23psi bypass pressure.
I think the short answer is that they didn't, it's just what that filter comes with. In my experience the bypass is there to protect the filter media, that's why it varies by the type of filter, because different materials can withstand different degrees of differential pressure. I agree unfiltered oil flowing through your engine would suck, but how would you like that unfiltered oil carrying hunks of your destroyed oil filter through the engine?
I know this is an old thread but for some reason, it popped up on my phone's news feed just yesterday. I'm sure someone will give me crap for reviving a year plus old thread.
After working in an industrial setting for a number of years, some of my experience has dealt with filtration; I'm willing to take a really **** good stab at your question regarding why Subaru chose the 23psi bypass pressure.
I think the short answer is that they didn't, it's just what that filter comes with. In my experience the bypass is there to protect the filter media, that's why it varies by the type of filter, because different materials can withstand different degrees of differential pressure. I agree unfiltered oil flowing through your engine would suck, but how would you like that unfiltered oil carrying hunks of your destroyed oil filter through the engine?
Purolator is not crap. Clearly everyone has a different opinion on this. If you read enough forums, not just Subaru, you will hear 'fram is the best, then 'fram is the worst' then ' fram is not what it used to be.' You will see comments like this about very brand. Car companies marketing is based on numbers. They cant just say out filter is better so they say it will last for 20k miles. If you believe a number like that, I have a bridge in Brooklyn to sell you. Did you know for many people the deciding factor for which car to buy is the number of cup holders? Quality and marketing crap are two different things.
I always run factory filters due to cost and peace of mind for a quality filter. Not sure about everyone else but the dealer around me charges $9 with a new crush washer. NAPA sells their filters for $11, K&N for $18, Walmart FRAM/Generic filters are $7. Non of these come with a crush washer so I still need to stop at the dealer and spend an extra $1.
It's a no brainer for a OEM filter.
It's a no brainer for a OEM filter.
Eh, I'm not exactly cheap, but I'm perfectly content with using whatever I decide is sufficient to get the job done (I always do my research and include a safety margin). The "5 dollar" stock Japanese filter has never been shown to be poorly constructed. All these fancy oils and filters, just like a lot of automotive products, are textbook examples of the subjective theory of value. It's nice to have choices.
Sort of the way most fishing tackle is designed to catch fishermen, not fish.
Anyway, just bought 4 OEM filters for $27 on Ebay, free ship/no tax.
Add that to my 4 jugs of Mobil 1 AFE 0w-20, $11/5 quart after rebate, I'm all set.
Thanks, but I'll change my oil for 20 bucks rather than pay 25 for an oil analysis to see if I can stretch it out.
My only issue with bumping this thread is that there's currently an active thread discussing the bypass spec (which includes a technical explanation of why it is specced as such).
Thats what kills me about the oil change cult I am seeing in places like BITOG, so many of these people getting UOA reports could just change their oil for the price they pay for a UOA.
I recently paid $6.75 for a Subaru OEM oil filter and $24.14 for a 5 quart jug of Mobil 1 AFE that has a $12 rebate. $18.89 total after rebate and I am good for 6000 miles with a 66 cent crush washer that I have a bag of.
Nickel and dime people driving themselves crazy I tells ya'
As this is not a “normal procedure” you may find it very difficult to get an authoritative answer to your question from members on this forum, unless someone else has actually done it of course.
Why don’t you try it and then you can post an answer to your question so that the rest of us will have the benefit of your experience.
As the filter is mounted above the sump I suspect you will probably lose up to a quart or two of oil BUT if the filter outlet sets up a vacuum flow through to the sump, you could potentially drain all the oil from the sump.
You could try using a shop vacuum over the oil fill port as this should prevent any additional oil loss beyond what is in the filter.
Seagrass
Why would you lose any more than you would removing the filter when doing a complete change?
To say nothing of them wanting to run their 2-stroke 50:1 equipment on a 100:1 mix. LOL
:29:
Joined
·
62 Posts
where to start....Most oil filters today do amazing job for what they were design--Hold dirt . If you not doing extended oil changes (10-12K km's or more) i don't see the need for expensive filters. 1 micron, 2 microns to me, all BS to sell overpriced filters. Any major brand and OEM filters will be just fine. Extended oil changes it's more about the quality of the filtration media than how small the microns it can hold. The vast majority of oil filter "failures" i have seen, was not filters fault at all. From filters installed with full plastic wrapper still on, to double gasket filters, wrong application, cut gaskets, missing gaskets, crazy over-tight filters.. I can remember very few instances of real failed filter, and those few; almost all was from the .59cent one size fits all bin. At end of the day, any good quality filter will be fine on an Outback. I guess Oil Filters and Oil brands are a sensitive issue for some
Must be, since there is a zillion post forum built on it! And everyone's an expert.I guess Oil Filters and Oil brands are a sensitive issue for some
I wanted to follow up, after having done extensive research on what has been discussed, to say that I am giving my personal recommendation to the Fram Ultra Synthetic oil filter. I have used this filter before on my Outback with good results but I too had been hung up on the 23psi bypass spec in the past.
One interesting piece of information I came across stated that the Fram Ultra XG7317 filter (used on Subaru 2.5L) has a max output of 18 gallons per minute, including tested verification. All of this info is easily found on BITOG, that and a discussion from all the way back in 2009 with a technical readout of all of Subaru's dread oil pump specs.
Of note is the specific reference to the specific oil filter utilized by Subaru to accomodate this oil pump. It very clearly states that the filter media is paper (cellulose) and it is well know that this type of filter media is flow restrictive as compared to the newer, more advanced synthetic filter media like say in a Fram Ultra Synthetic oil filter. So I deduce that the Subaru OEM oil filter has a 23psi bypass due to the filter media that allows for a max flow rate of 14.5 gallons per minute. WIX/NAPA uses a 27psi bypass and I deduce that it is because their filters are limited to a 10 gallon per minute flow rate perhaps due to the size specs of their filters, media, etc.
My conclusion is that the bypass spec is determined by the variables of a SPECIFIC FILTER which means not all are required to have the same bypass spec to function as intended. Lower flow rate = higher bypass (ie WIX/NAPA), higher flow rate = lower bypass (ie Fram Ultra). Based on the test information I have seen on the Fram Ultra its flow rate is so high that it effectively cuts the PSID in half when used with an appropriate oil, that means that the Ultra's 13 psi bypass is equivalent to or even exceeds the WIX/NAPA 27psi bypass.
One interesting piece of information I came across stated that the Fram Ultra XG7317 filter (used on Subaru 2.5L) has a max output of 18 gallons per minute, including tested verification. All of this info is easily found on BITOG, that and a discussion from all the way back in 2009 with a technical readout of all of Subaru's dread oil pump specs.
Of note is the specific reference to the specific oil filter utilized by Subaru to accomodate this oil pump. It very clearly states that the filter media is paper (cellulose) and it is well know that this type of filter media is flow restrictive as compared to the newer, more advanced synthetic filter media like say in a Fram Ultra Synthetic oil filter. So I deduce that the Subaru OEM oil filter has a 23psi bypass due to the filter media that allows for a max flow rate of 14.5 gallons per minute. WIX/NAPA uses a 27psi bypass and I deduce that it is because their filters are limited to a 10 gallon per minute flow rate perhaps due to the size specs of their filters, media, etc.
My conclusion is that the bypass spec is determined by the variables of a SPECIFIC FILTER which means not all are required to have the same bypass spec to function as intended. Lower flow rate = higher bypass (ie WIX/NAPA), higher flow rate = lower bypass (ie Fram Ultra). Based on the test information I have seen on the Fram Ultra its flow rate is so high that it effectively cuts the PSID in half when used with an appropriate oil, that means that the Ultra's 13 psi bypass is equivalent to or even exceeds the WIX/NAPA 27psi bypass.
Just to add something to a bypass pressure specific oil filter thread - Subaru is not unique in that regard, and it's not just for some spurious reason. Also consider that "flow rate" depends on viscosity and viscosity changes with temperature and different oil grades have different viscosity, so any given X gallons per minute spec for filtering media is for a given viscosity oil at a given temperature (and pressure). Using a low bypass pressure filter at low temperatures with high viscosity oil is a worst case scenario for cold start filter bypass.
GM switched to 22 psi bypass pressure spec and the linked TSB explains why.
BITOG thread about it: Wix updates Gen V oil filter specs - 22 PSI bypass
In 2009 with the Series 2 RX-8, Mazda changed from a low bypass pressure to high (20+ psi) bypass pressure filter, at the same time that they changed their oil pump to a higher flow one. (Subarus also have high flow oil pumps)
Isuzu also switched to a higher (unspecified) bypass pressure oil filter but cautions not to use it on vehicles that were specified for a low bypass pressure because of potential oil starvation.
All I'm saying is that bypass pressure isn't something that only Subaru is some quirky unicorn manufacturer that out of pure randomness ended up with this 20+ psi bypass spec and has just stuck with it out of inertia.
Other manufacturers have followed Subaru in going to higher bypass pressure filters, and for cold-start reasons - but this does not mean that a higher bypass pressure is always better.
GM switched to 22 psi bypass pressure spec and the linked TSB explains why.
BITOG thread about it: Wix updates Gen V oil filter specs - 22 PSI bypass
In 2009 with the Series 2 RX-8, Mazda changed from a low bypass pressure to high (20+ psi) bypass pressure filter, at the same time that they changed their oil pump to a higher flow one. (Subarus also have high flow oil pumps)
ONLY USE GENUINE Mazda OIL FILTERS in Series II (R3) - RX8Club.com
Series II Technical and Trouble shooting - ONLY USE GENUINE Mazda OIL FILTERS in Series II (R3) - Series II RX-8 owners... I have noticed many aftermarket brands of Oil Filters are still recommending the same OIL Filter that is used on the Series 1 RX-8's...TOTALLY INCORRECT. You may not be...
www.rx8club.com
Isuzu also switched to a higher (unspecified) bypass pressure oil filter but cautions not to use it on vehicles that were specified for a low bypass pressure because of potential oil starvation.
All I'm saying is that bypass pressure isn't something that only Subaru is some quirky unicorn manufacturer that out of pure randomness ended up with this 20+ psi bypass spec and has just stuck with it out of inertia.
Other manufacturers have followed Subaru in going to higher bypass pressure filters, and for cold-start reasons - but this does not mean that a higher bypass pressure is always better.
Our member @Mott Power posted a most excellent explanation in a thread I came across recently:
"The bypass setting is based on PSID; the difference between the inlet and outlet pressure of the filter, not in relation to absolute pressure from the oil pump (which is variable to rpm). Meaning the bypass opens if the difference in pressure prior to the filter is greater than 23 psi compared to the pressure after the oil filter, no matter if you're measuring 25 psi or 60 psi to the filter.
If you're running 40 psi from the pump, that doesn't mean the oil filter is bypassing all oil after 23 psi. Rather, if the inlet pressure to the filter is 40 psi and the outlet pressure is 17 psi, then it will open (similar in some regards to how intake bypass valves operate on turbocharged vehicles). N4HHE & idosubaru were right on the money in regards to their posted explanations.
Oil filter bypass numbers are a factor of the flow rate of the filter element (surface area and density) vs the viscosity of the oil. Oil viscosity is a constant at 0w-20 for our vehicles. If you change the filter element's flow rate, then you can variably adjust the bypass setting. Hence why some manufacturers have lower ratings but still call for it be used on our Outbacks. This doesn't mean they will operate in bypass "99% of the time"... It will function virtually the same way, but the argument you run into is how much of the particulates are being filtered if it has a higher or lower flow rate through the element (whole other discussion...).
Subaru's oil pressures are not much different than other systems; I have measured flow rates on various other cars and it's not much different from what the service manual states."
www.subaruoutback.org
"The bypass setting is based on PSID; the difference between the inlet and outlet pressure of the filter, not in relation to absolute pressure from the oil pump (which is variable to rpm). Meaning the bypass opens if the difference in pressure prior to the filter is greater than 23 psi compared to the pressure after the oil filter, no matter if you're measuring 25 psi or 60 psi to the filter.
If you're running 40 psi from the pump, that doesn't mean the oil filter is bypassing all oil after 23 psi. Rather, if the inlet pressure to the filter is 40 psi and the outlet pressure is 17 psi, then it will open (similar in some regards to how intake bypass valves operate on turbocharged vehicles). N4HHE & idosubaru were right on the money in regards to their posted explanations.
Oil filter bypass numbers are a factor of the flow rate of the filter element (surface area and density) vs the viscosity of the oil. Oil viscosity is a constant at 0w-20 for our vehicles. If you change the filter element's flow rate, then you can variably adjust the bypass setting. Hence why some manufacturers have lower ratings but still call for it be used on our Outbacks. This doesn't mean they will operate in bypass "99% of the time"... It will function virtually the same way, but the argument you run into is how much of the particulates are being filtered if it has a higher or lower flow rate through the element (whole other discussion...).
Subaru's oil pressures are not much different than other systems; I have measured flow rates on various other cars and it's not much different from what the service manual states."
Oil filter other than SUBARU brand?
Nope. The "rule of thumb" benchmark for many years was 10 psi per 1,000 rpm. From the 2015 Legacy/Outback Factory Service Manual, FB25 engine: 2-stage pressure control valve 1st stage opening pressure = 21.7 psi Main opening pressure = 82.6 psi Pressure at 600 rpm: >5.8 psi Pressure at 6,000...
www.subaruoutback.org
I agree with everything in that post above - the bypass is for pressure differential within the oil filter, which is in effect the pressure difference before and after the filtering medium. 80 psi in, 60 psi out, is 20psi differential. 25 psi in, 5psi out, is also 20 psi differential.
The bypass pressure is the maximum pressure drop (difference) that the filter can produce before the bypass beings to open. Because the oil pump is positive displacement, the pressure drop isn't lowering the pressure after the filter, but increasing the pressure in front of the filter.
Reasons for increased pressure differential are that the filtering medium is clogged, or that the fluid passing through the filtering medium is too viscous for the flow rate through the filtering medium. Either one would increase pressure differential.
For a given viscosity and filtering medium, increasing flow rate will increase pressure differential. The positive displacement oil pump increases flow rate with RPM.
So you will get bypass based on an equation that relates to flow rate, viscosity, and resistance of the filtering medium.
The bypass pressure is the maximum pressure drop (difference) that the filter can produce before the bypass beings to open. Because the oil pump is positive displacement, the pressure drop isn't lowering the pressure after the filter, but increasing the pressure in front of the filter.
Reasons for increased pressure differential are that the filtering medium is clogged, or that the fluid passing through the filtering medium is too viscous for the flow rate through the filtering medium. Either one would increase pressure differential.
For a given viscosity and filtering medium, increasing flow rate will increase pressure differential. The positive displacement oil pump increases flow rate with RPM.
So you will get bypass based on an equation that relates to flow rate, viscosity, and resistance of the filtering medium.
41 - 60 of 107 Posts
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
