Subaru Oil Pump Specs as Relates to Filter Bypass

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Originally Posted By: Gary Allan
I guess you will make me go through all the hardware rigging. I had a great platform to do this lame stuff on with my minivan ..but it goes stolen ..with a good bit of my hardware in it.

..but if you insist.. I will show you low volume with high differential at cold temps ..and I will show you high volume at cold temps with virtually no differential. I will also show you high volume with virtually no differential.

You'll have one out for weasel room. I won't be able to quote volume ..but ..if we're genuinely trying to work on "seeing" ..you'll forgo the opportunity to skate.
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How do you think I came up with all this? Just pulled it out of my behind?
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No, pal. It's REAL
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But your missing the whole point ... it's the VOLUME that's going to make or break this whole discussion. It's the volume in question that makes this situation different than in most cars on the road. Any engine that puts out tons of oil volume is going to have to use a filter that is capable of working correctly in that environment. What kind of filters are used on race cars that put out tons of oil volume? Tell you something.

My whole point here is that the Subaru's oiling system under discussion has uncommonly high volume output for a road car.

If the pump puts out high volume under hot conditions (per the spec), then it will also put out a relatively high volume output under cold oil conditions, as compared to other vehicles. That's because the oiling system is much more unrestrictive than what you are use to seeing and playing with. An unrestrictive system will flow more cold oil than a restrictive one ... and that means the filter used on it will also have to handle a higher cold oil flow volume.

Can you get your head around on just how much 12.4 gpm is? - that's like a wide open garden hose flowing. If the engine only holds say 5 quarts, that means the entire sump volume is exchanged nearly 10 times every minute if the engine was running at 5000 RPM. That's HUGE, and yes somewhat hard to believe - but we have to believe Subaru's specs unless proven false somehow.

If the system on that engine can flow 12.4 gpm with 176 deg F oil, and it only requires 43 psi of supply pressure to do so (much less than the pump's relief pressure setting), then the oiling system can not be a very restrictive compared to some other cars. In fact, it even has some margin in it's performance to flow the full 12.4 gpm with oil colder than 176 deg F, meaning you could increase the oil viscosity to the point until the pump bumps up against its 85 psi relief setting to push the 12.4 gpm through the system.

I think you are under the impression that this oiling system is like 99% of all the others on the road ... forget what you think it should do and look at what it does based on the specs from Subaru.

If you did a test where you could flow 12.4 gpm of oil (at say whatever oil temp keeps the pump just a hair below the 85 psi relief setting), I'm sure you'd see MUCH MORE than a few PSID across the element. That's why Subaru has specified a 23 psi filter bypass setting (at least on their specific OEM filter), so that they ensure the bypass doesn't open when it shouldn't.
 
Originally Posted By: LoneRanger

Wix filter for my car is 51365 with bypass rated at 8-11 psi, plus it appears to be a universal filter hence the lawn tractors and outboard marine motors it also is purported to fit:

http://www.wixfilters.com/filterlookup/ResultsPart.asp?PartNo=51365

Click the part number for a pop-up with specs and fitment for the filter.

I removed the Wix 51365 this past week after this discussion made me increasingly uncomfortable with the low bypass setting.

I now have one of the OE Subaru filters on again, the Honeywell made blue ones-- local dealer sells them for $6... cheap compared to what other Subaru dealers are charging for them. Filter changes are mess-free and super easy on this car.



I'm familiar with that filter, it's the same one called out for my V6 Altima engine (VQ35DE). I just bought the longer version for my next oil change (NAPA Gold 1356, which would be the WIX 51356) since I have enough room to run a longer filter. Can you use the longer filter? ... I think I remember you saying you can't due to clearance issues.

After looking at the oil pump specs on your Subaru, I'd also be a little nervous using a non-OEM filter unless I got specific word from the filter manufacture’s Engineering Department that they understand the oil pump on that car is high volume, and the filter has been verified to work correctly. It could be that they don't care much because after the oil warms up the filter would probably work just fine and they figure that some cold oil bypass is acceptable without any major ill effects. Hard to say exactly what's in the minds of these filter designers sometime.

If you contact WIX or whoever, I'd be interested in hearing their inputs on this one.
 
If anyones wants to see where I drew these specs from PM me an email addr and I can email the PDF file that has this info in it.
 
To add another dimension to the OE filter vs Wix 51365 comparison as has surfaced in this discussion, here is a picture of a new unused Wix 51365's filter element compared to a used Subaru blue OEM (Honeywell) filter element after both cans were cut open (w/a hack saw-- kind of sloppy but it worked... chewed up the Honeywell's end cap a bit):

IMG_0832.jpg


As can be seen, the OE filter appears to feature more media. which only seems to hurt the case against using the Wix in this car even more as smaller media area = higher PSID but with a bypass setting almost 1/3 the strength of the OE spec.
 
Originally Posted By: LoneRanger
Originally Posted By: SuperBusa
LoneRanger - are there any filter manufactures (such as WIX, K&N, M1, etc) that actually have a filter specified for your Subaru? If so, then I would certainly think that they know it has a high volume oiling system and have designed the filter accordingly. If they made a filter, it certainly wouldn't hurt to contact their Engineering Tech Dept to get their inputs to your concern.


Wix filter for my car is 51365 with bypass rated at 8-11psi, plus it appears to be a universal filter hence the lawn tractors and outboard marine motors it also is purported to fit:

http://www.wixfilters.com/filterlookup/ResultsPart.asp?PartNo=51365

Click the part number for a pop-up with specs and fitment for the filter.

I removed the Wix 51365 this past week after this discussion made me increasingly uncomfortable with the low bypass setting.

I now have one of the OE Subaru filters on again, the Honeywell made blue ones-- local dealer sells them for $6... cheap compared to what other Subaru dealers are charging for them. Filter changes are mess-free and super easy on this car.



I did the same thing on my 2001 H6 which also needs a filter with the 23psi bypass(when I'm at my desktop, I'll post the specs for the oil pump/filter for that car - I have the service manual pdf on that computer). The car has a 6 litre oil capacity.

I had been using a Wix filter on my car as well, but switched back to the Canadian Subaru filter (when you say Honeywell, you really mean FRAM right - you just can't bring yourself to type that four letter word haha).

Speaking of filters for Subaru's - I replaced the tranny filter (which is a spin-on) with a Wix as well. I see the bypass on the Wix tranny filter is also 8-11psi. I wonder if I should switch this filter back to Subaru? One big difference is that on the Subaru tranny filter, there is a fine metal mesh screen AFTER the bypass filter. I assume this is to catch any larger debris that might blow out when the filter goes into bypass mode. I would hazard a guess that this filter is also a FRAM.
 
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Quote:
it's the VOLUME that's going to make or break this whole discussion.


Naturally. It's the only thing to leave out
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It's the volume in question that makes this situation different than in most cars on the road.


Yes. So do you now concede to things that you've been avoiding like the plague?
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Let's "qualify" your statements. It's ONLY in this or like situations that a filter has any merit in terms of resistance or restriction, correct??
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the rest was a waste of typing. Captain Obvious to my rescue.


Except maybe this:

Quote:
That's why Subaru has specified a 23 psi filter bypass setting (at least on their specific OEM filter), so that they ensure the bypass doesn't open when it shouldn't.



Cold start relief events: MANY

5000rpm 12.4gpm events: FEW

Likely duration of dwell time in bypass

Cold start relief events: MANY

5000 rpm 12.4 gpm events: FEW

Likely sensible benefit to a high bypass valve setting????
 
Originally Posted By: Gary Allan
Quote:
it's the VOLUME that's going to make or break this whole discussion.


Naturally. It's the only thing to leave out
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Quote:
It's the volume in question that makes this situation different than in most cars on the road.


Yes. So do you now concede to things that you've been avoiding like the plague?
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I've said that from the first few posts in this thread. It's not a matter of me "condeding", but more of a matter of your reading comprehension.
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Originally Posted By: Gary Allan
Let's "qualify" your statements. It's ONLY in this or like situations that a filter has any merit in terms of resistance or restriction, correct??
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the rest was a waste of typing. Captain Obvious to my rescue.


Huh ... agian, you're just realizing this? Where have you been? Please, go back and read this thread about 3 times ... it might sink in then. I've qualified my disussion in this thread in every manner possible. Let me say it one more time ... it's all a matter of flow VOLUME in this case. More flow VOLUME means more filter PSID, which means the filter bypass needs to be set higher accordingly for all possible use senarios ... including cold starts and running the engine during oil warm up period.


Originally Posted By: Gary Allan
Except maybe this:

Quote:
That's why Subaru has specified a 23 psi filter bypass setting (at least on their specific OEM filter), so that they ensure the bypass doesn't open when it shouldn't.



Cold start relief events: MANY

5000rpm 12.4gpm events: FEW

Likely duration of dwell time in bypass

Cold start relief events: MANY

5000 rpm 12.4 gpm events: FEW

Likely sensible benefit to a high bypass valve setting????



Actually, it would NOT flow 12.4 gpm when the oil is cold ... I thought we already established this point. Every thing you've parroted has already been painstakingly explained (for your benefit – or was it to give you a reason to counter argue every point) in my previous posts.

The fact still remains that Subaru has set the filter bypass to 23 psi for a specific reason ... not just to be different from everyone else. The reason is because of the high volume oil pump and the free flowing oil system on this engine. I've explained it every which way I can ... anything else is a waste of time.
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So, it sounds like your suggestion is to put whatever oil filter on this car and not worry about it? … that seems kind of careless to me.

If it was my car, I’d run the OEM filter. I’d contact the Engineering Dept of anyone who actually lists a filter for this specific car and ask them to prove to me that they have accounted for the high oil pump volume on this application. Otherwise, I’d be leery of just throwing any oil filter on it.

Either that, or just don't rev the engine much until the oil is pretty hot ... but who want's to screw with that all the time?
 
Originally Posted By: LoneRanger
To add another dimension to the OE filter vs Wix 51365 comparison as has surfaced in this discussion, here is a picture of a new unused Wix 51365's filter element compared to a used Subaru blue OEM (Honeywell) filter element after both cans were cut open (w/a hack saw-- kind of sloppy but it worked... chewed up the Honeywell's end cap a bit):

IMG_0832.jpg


As can be seen, the OE filter appears to feature more media. which only seems to hurt the case against using the Wix in this car even more as smaller media area = higher PSID but with a bypass setting almost 1/3 the strength of the OE spec.


I've seen filters on 600cc motorcycles bigger than that! There might be a slight illusion here though ... I'd bet the metal end caps only cut some of the effective filer area; less than what it appears like.

So I take it you can't use the 51356 which has the same filter specs, but about 1" longer? Of course the bypass is still 8-11 psi on that one, so I'd still be leary until further info could be obtained from WIX.
 
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So, it sounds like your suggestion is to put whatever oil filter on this car and not worry about it? … that seems kind of careless to me.


I dunno. Maybe "I" wouldn't worry about it. Then again, I use 0w-10 oil, so what do I know
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You're just getting fall out from our last slug fest, that's all.
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In evaporators, it's called "carry over".
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Quote:
Actually, it would NOT flow 12.4 gpm when the oil is cold


Let's read this again ...for clarity ...

Cold start relief events: MANY

5000rpm 12.4gpm events: FEW

Likely duration of dwell time in bypass

Cold start relief events: MANY


I don't see any reference to 12.4gpm of cold flowing oil, just cold start events. Do you really see it (imagine a piece of paper that I flip over and examine both sides ..several times ..and blink as though to clear my eyes)
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Originally Posted By: Gary Allan
Quote:
So, it sounds like your suggestion is to put whatever oil filter on this car and not worry about it? … that seems kind of careless to me.


I dunno. Maybe "I" wouldn't worry about it. Then again, I use 0w-10 oil, so what do I know
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You're just getting fall out from our last slug fest, that's all.
grin2.gif
In evaporators, it's called "carry over".
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Quote:
Actually, it would NOT flow 12.4 gpm when the oil is cold


Let's read this again ...for clarity ...

Cold start relief events: MANY

5000rpm 12.4gpm events: FEW

Likely duration of dwell time in bypass

Cold start relief events: MANY


I don't see any reference to 12.4gpm of cold flowing oil, just cold start events. Do you really see it (imagine a piece of paper that I flip over and examine both sides ..several times ..and blink as though to clear my eyes)
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I don't see any statement saying the oil is hot either. And why would you worry about 12.4 gpm at 5000 RPM with hot oil anyway? ... didn't we conclude (more than once) that is an operating condition that is not as critical as cold starts and high engine RPM during oil warm-up phase? Don't weasel out here ... are you studying to become a kangaroo court lawyer in your spare time?
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Quote:
I don't see any statement saying the oil is hot either.


Well, we've probably both figured out that you probably couldn't push 12.4 gpm of cold oil through the engine ..you would be in a relief event (most likely) ...and that's where we're nearer the "cold start" scenario.

Quote:
didn't we conclude (more than once) that is an operating condition that is not as critical as cold starts and high engine RPM during oil warm-up phase?


I didn't see any conclusion on your part (I may have lost it in the salvos). I've seen you repeatedly cite the hot oil 12.5 gpm scenario to bolster your pressure/restriction POV ..and, in implication, attempt to apply it over the full span of operation. ..or did I get that wrong?
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Quote:
are you studying to become a kangaroo court lawyer in your spare time?


Debate is an art, my friend. I do thank you for challenging me at my limits. The art of winning any debate is conceding to the obvious and passing over it and moving on to promote your POV with reasons that show its advantages/strengths. You'll note my repeated (and ignored) references to "granted and conceded to". You went on to treat me as a plebe on primary fundamentals of differentials and pressures, bogging the discussion down in needlessly redundant information ..while never attacking my basic way of viewing the events as they occur. "Let's get beyond this and see if you can manage this" fell on deaf ears.

I was sitting there with my partner and we had a problem with the evaporator and he couldn't understand it. I blurted out as close a parallel scenario in another system as I could in an attempt to get him to relate to what was going on. He gave me some static about the lack of contour to what was at hand. I then said, "For a minute ..pretend that you actually want to understand what I'm saying and not engage in an argument". He paused ..and nodded his head in understanding. He had to choose to employ the abstract thought process. It wasn't a natural act for him. For me, it's FIRST nature.

This is how I've rationalized these physical events. If you're going to install a new paradigm for me, you're going to have to work from within my understanding and make it not work. For that, you'll first have to attempt to see how I've got where I am and then prove that pathway to be in error. I can't think too much outside of the box that I've constructed. I don't have the disciplined back ground to do so.
 
Originally Posted By: Gary Allan

Quote:
didn't we conclude (more than once) that is an operating condition that is not as critical as cold starts and high engine RPM during oil warm-up phase?


I didn't see any conclusion on your part (I may have lost it in the salvos). I've seen you repeatedly cite the hot oil 12.5 gpm scenario to bolster your pressure/restriction POV ..and, in implication, attempt to apply it over the full span of operation. ..or did I get that wrong?
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The conclusion is buried in here somewhere – you just skim over some of this stuff I’m willing to bet. The “bolstered” examples were to show just how much flow volume the filter would have to take on in a max flow case ... which is obviously hot oil without any pump relief - or even just warm oil since the pump isn’t near the 85 psi relief at quoted flow spec. Since the 12.4 gpm flow spec was quoted at 43 psi, and the pump relieves at 85 psi, then all 12.4 gpm will go through the filter. IMO, that is one reason the filter’s bypass is set to 23 psi ... because 12.4 gpm, even with warm oil, is a HUGE flow rate compared to some engines and can create a pretty significant PSID. Of course, there could be a worse case than that if whatever flow rate (in gpm) you can get through the filter with cold oil with 85 psi pushing it through the system. The higher viscosity at a much reduced flow rate would probably cause the highest PSID case. Of course, without doing some heavy duty number crunching, or and actual flow test one would not know for sure.

What do you think a typical say LSx GM V8 engine flows at near redline? I guess I could get my factory service manual out and see ... but I’d be very surprised if it is near 12.4 gpm at max flow conditions. Of course, most GM V8s use a somewhat larger filter than the Subaru in this discussion, so that alone helps the designed bypass PSI setting come down some.

Originally Posted By: Gary Allan
Debate is an art, my friend. I do thank you for challenging me at my limits. The art of winning any debate is conceding to the obvious and passing over it and moving on to promote your POV with reasons that show its advantages/strengths.


Humm ... seems more than not you will challenge the obvious described by me, just to put it in your own words – or many you don’t quite grasp the concept because it’s not described in a manner you expect (?). This is what makes these round ‘n round discussions (on both our parts) at times one big cluster [you know what].
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Quote:
What do you think a typical say LSx GM V8 engine flows at near redline? I guess I could get my factory service manual out and see ... but I’d be very surprised if it is near 12.4 gpm at max flow conditions. Of course, most GM V8s use a somewhat larger filter than the Subaru in this discussion, so that alone helps the designed bypass PSI setting come down some.


It's probably quite high. I don't know if it would be in the 12gpm realm ..but I wouldn't be surprised with 10+/-.

We keep defaulting to the ultra ubber here.

You're new, so you haven't heard ..literally thousands of times... "I've purchased XYZ filter because it flows better" when flow is not a function of the filter. It's a function of the pump.

It's the difference of two people viewing "I chose 10w-40 so it would be thicker when hot and thinner when cold". While I'm giving orientation on the fact that the cold spec is VERY THICK (which would not be apparent in the static statement without qualification) ..you're up there on the 40 weight properties.

Quote:
Humm ... seems more than not you will challenge the obvious described by me, just to put it in your own words – or many you don’t quite grasp the concept because it’s not described in a manner you expect (?).


I see said the reflection in the mirror.
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After lurking around this site for several years and recently registering I'm compelled to make my first post. I have 2 Subies to maintain and found this a very interesting discussion, though much was far over my head.

I wrote to customer service at Hastings and this is the reply, though not technically helpful I found it to be an honest statement FWIW.

Recently there has been a bit of discussion on Subaru lube filters and the Subaru oil system on enthusiasts forums. The gist is that Subaru recently announced a new filter which the user community believes is produced by Honeywell (Fram) to Subaru specifications. Frankly, there is not much happiness in this new product. The discussion on the oil system indicates that Subaru uses a high volume oil pump and specifies a 23 PSID pressure relief valve.
I have two Subaru cars with the 4 cylinder 2.5 liter non-turbo engine. Both use a LF113 (or the longer LF240). My search through the various filter manufacturers' sites (Hastings/Baldwin, Wix, Fram, and Purolator) reveals that no filters, searched for my application, contains the 23 PSID pressure relief valve as specified. My primary concern is cold flow on startup as these are daily drivers - not a performance application. I use 5w-30 oil as recommended by the owners manual.
Should I be concerned about the difference between the 14 PSID spec on the LF113 and the factory spec of 23 PSID? Is there any technical reason the correct pressure relief is not available? Are there any plans to offer a filter with the correct specification?

Thanks in advance for your help. It is quite bewildering to have this great a variance in specifications.


REPLY:
Thank you for using Hastings Filters. I do not recommend using a filter with a 14-16 psi bypass valve in an application which calls for a filter with a 23 psi by-pass valve. We design our filters with a 3 psi maximum tolerance with regards to bypass valves. Therefore, I doubt that we would cross the new Subaru number to either the LF113 or the LF240. We do have a very similar filter with a 20 psi bypass valve. This is the LF491. If you have further questions, please feel free to contact me.
Cordially,

TRAVIS R. WINBERG
SUPERVISOR OF SERVICE ENGINEERING
 
Originally Posted By: Gary Allan
Quote:
What do you think a typical say LSx GM V8 engine flows at near redline? I guess I could get my factory service manual out and see ... but I’d be very surprised if it is near 12.4 gpm at max flow conditions. Of course, most GM V8s use a somewhat larger filter than the Subaru in this discussion, so that alone helps the designed bypass PSI setting come down some.


It's probably quite high. I don't know if it would be in the 12gpm realm ..but I wouldn't be surprised with 10+/-.


I've got the factory service manual for a 2002 LS1/LS6, so I'll see if it has any oil system specs listed.

Originally Posted By: Gary Allan
You're new, so you haven't heard ..literally thousands of times... "I've purchased XYZ filter because it flows better" when flow is not a function of the filter. It's a function of the pump.


That statement is way too general, or just plain wrong.
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In actuality, the flow volume THROUGH THE SYSTEM (which includes the filter) is a function of the pump's supply pressure AND the flow circuit resistance. Yeah, the pump's output performance has a bearing on the system flow, but so does the flow circuit's resistance which includes the filter (PSID). IF a filter is indeed was very restrictive, then it WILL effect the flow volume going through the engine - especially if the oil is cold or is very high volume. For some reason you can't seem to grasp this concept
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- please tell me you're on the same page here. You have to look at the entire SYSTEM to see what's going on. If you have a constant pump supply pressure, then the oil flow will choke down more and more through the circuit as the restriction to flow increases. The ONLY way a filter will NOT affect the oil flow going through an engine is if it has zero flow PSID (impossible) or the bypass is set to zero (doubt it).

Man in the mirror looking ... humm.
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WagonBoss - interesting reply from Subaru, and right in line with the discussions here. So glad you joined in, and amazing that it took a wild thread like this one to get you to post.
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Originally Posted By: Subaru Tech Dept
I do not recommend using a filter with a 14-16 psi bypass valve in an application which calls for a filter with a 23 psi by-pass valve. We design our filters with a 3 psi maximum tolerance with regards to bypass valves.


The high volume pump is the reason why Subaru recommends using a filter with the 23 psi bypass setting. They understand that with higher volume of oil going through the filter, that there is a corresponding higher pressure drop across the element and have taken measures to ensure less filter bypass occurances. If they only have a 3 psi max tolerance (ie, "headroom") on the bypass setting, then they expect to see 20 PSID events across the filter element - at least that's how I read it.
 
Just for clarity the reply was from Hastings Filter - not Subaru. I found it interesting they aren't recommending the filter they say is the correct filter for the application.
 
Couple points...

At almost 50 quarts of oil per minute, would you not expect the pump to literally suck the sump empty?? Sorry, but the oil doesn't return to the sump that fast in the real world as it gets hung up on things...

And do you REALLY think you are using almost 50 quarts per minute?? Think about the clearances...while the pump might be able to flow that much oil, its doubtful the engine (even in a completely worn out scenario) would flow that much oil...

If the clearances actually allowed that much flow, the engine would starve of oil at an idle...
 
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