Oil Filter Flow Rate vs. Filtering Efficiency - Can You Have Both ?

[Ignatius]

OK maybe I am a bit colorblind. I do not know what is the bypass setting on Royal Purple is iether, but it is 13 PSI on Fram. That means under normal operating conditions, at least on a Subaru Outback which is14.7 GPM, the Ultra will be in bypass because at anything over 13 GPM the Ultra will be in bypass.

In a Subaru it would more than be tested, a brand new FRAM Ultra would be in bypass at well below max RPM. Operating anywhere under redline is normal operating conditions, else Subaru would have lowered redline to say, 4,000 RPM. It would be interesting to see how the delta P of these filters increases after 5,000 or 10,000 miles in service but it is only going to increase as the filter loads up, not to decrease.

You were right though this test result should settle the matter why Subaru sets its bypass spec high, to 23 PSI or 27 PSI. Now maybe we should look for filters that say they are “recommended” for Subaru but whose filters have bypass PSI set so low that a brand new filter of theirs easily goes into bypass.

Can you actually tell us how you are coming up with these conclusions instead of simply repeating them as if that made them true and accurate? This is the second time I have asked you this in this thread. Here is a link to a series of links I have daisy chained on this exact subject:

https://bobistheoilguy.com/forums/threads/subaru-vs-wix.273392/post-5241507

 

[ZeeOSix]

OK maybe I am a bit colorblind. I do not know what is the bypass setting on Royal Purple is iether, but it is 13 PSI on Fram. That means under normal operating conditions, at least on a Subaru Outback which is14.7 GPM, the Ultra will be in bypass because at anything over 13 GPM the Ultra will be in bypass.

Exactly which Fram model number are you talking about? Or exactly what year and model Subaru? I wouldn't call the pump putting out 14.7 GPM "normal operating conditions" unless you're driving around at redline all the time.

 

[Job]

You are not factoring in differential pressure, you are free to believe me or not but based on my near extensive research on the subject the unsaturated media flow rate of the Ultra effectively cuts the PSID in half as far as delta P across the media. By my estimation you would need to use this filter beyond two consecutive oil change intervals before the bypass boogeyman factor would come into play.

Being a bypass valve enthusiast myself I am using a Wix 57055 or Napa Gold 7055 on my 2021 Outback at every oil change and just not worrying about it.

Please provide references, proof, links, and pictures, or it isn true. It’s just a statement otherwise. Please explain unsaturated media flow rate of the Fram Ultra cuts the PSID in half for the dense like me. Thank you.
GMVN!

 

[ZeeOSix]

The real question is ... what is the delta-p vs flow curve for the Subaru OEM filters?

 

[ZeeOSix]

In the Subaru Outback, the service manuals says the oil pump in the FB25 engine puts out 14.5 GPM at 6,000 rpm.

Question is, will that much oil flow actually go through the engine without the pump going into pressure relief? Or is that the unregulated flow rate capability of the pump? There could be a big difference between those two things. As soon as the pump hits pressure relief the flow going into the engine is cut back a lot.

 

[wdn]

I suppose you could find all those answers yourself rather than ask somebody else to look it up for you. But since I had a spare minute or teo goes. This is from a 2018 thread on Bob. The engine I mentioned earlier was the garden variety normally aspirated 2.5L 4 late model Outback.

here is FA20DIT Engine 15.9 call it 16 GPM. Relief valve pressure of oil pump, 102 PSI.

 

[ZeeOSix]

I suppose you could find all those answers yourself rather than ask somebody else to look it up for you. But since I had a spare minute or teo goes. This is from a 2018 thread on Bob. The engine I mentioned earlier was the garden variety normally aspirated 2.5L 4 late model Outback.

here is FA20DIT Engine 15.9 call it 16 GPM. Relief valve pressure of oil pump, 102 PSI.

I'm really not interested in digging up data for a vehicle I don't own. Again, not totally clear if that oil pump spec is based on an unregulated pump or not. Obviously it's not going to flow that much as the oil becomes thicker because the pressure relief valve would kick in at some point. Notice the spec is at 120 deg C which means the oil is pretty thin, so maybe that's the flow with that temperature/viscosity of oil when the pump hits pressure relief at 102 psi.

Bottom line is use a filter specified for a Subaru ... and if particularly paranoid, use the OEM filter.

 

[wdn]

The real question is ... what is the delta-p vs flow curve for the Subaru OEM filters?

That’s not the real question it’s “a” question. Not a bad question. It’s a fair assumption that Subaru filter meets Subaru’s spec which is 27 PSI bypass valve on the oil filter itself. But Fram does not meet that spec.

Exactly which Fram model number are you talking about? Or exactly what year and model Subaru? I wouldn't call the pump putting out 14.7 GPM "normal operating conditions" unless you're driving around at redline all the time.

2018 Subaru Outback Fram Ultra XG7317, bypass valve setting 13 PSI

Not the highest GPM Subaru engine either. That is the sedate old Outback. That graph we are both looking at does not even cover the entire operating range of Subaru engines.

 

[ZeeOSix]

That’s not the real question it’s “a” question. Not a bad question. It’s a fair assumption that Subaru filter meets Subaru’s spec which is 27 PSI bypass valve on the oil filter itself. But Fram does not meet that spec.

It's the real question in order to know the real story about the OEM filter's flow performance (flow vs delta-p curve). I guess you can assume it's fine because it's an OEM filter ... that's about all you can glean. Like said, stick with the OEM Subaru filter if you don't like the bypass setting on aftermarket filters.

 

[wdn]

The WIX filter meets the bypass spec put forth by Subaru and its NAPA Gold equivalent does too. The Fram Ultra most definitely does not. The graph that you and I are apparently the only two people on here who know how to convert its units to GPM and PSI, shows it will hit and surpass the bypass rating of the Fram at least, when installed in a Subaru.

 

[wdn]

For those who joined late this is the graph ZeeOSix and I were discussing

 

[ZeeOSix]

For those who joined late this is the graph ZeeOSix and I were discussing

Also take note of what the test oil viscosity is during the ISO delta-p vs flow test - Post #144.

Would you all like to see ISO 4548-12 Oil Filter Lab Testing Comparison, Efficiency & Capacity, Pressure vs Flow, Bubble Point, and Burst?

Most manufacturers will choose a terminal Delta P that is known that will just hit the Delta P inflection point prior to instability. In the case of R and D that Delta P may not be known, thus increasing the window size, lowering or raising the overall efficiency. This unstable section should...

bobistheoilguy.com

 

[ZeeOSix]

The WIX filter meets the bypass spec put forth by Subaru and its NAPA Gold equivalent does too. The Fram Ultra most definitely does not. The graph that you and I are apparently the only two people on here who know how to convert its units to GPM and PSI, shows it will hit and surpass the bypass rating of the Fram at least, when installed in a Subaru.

Like I said, if you don't think an aftermarket filter will cut it on a Subaru, then either use the OEM or an aftermarket filter with a bypass valve set high enough to make you happy. I'm not here to say any specific aftermarket filter is going to work good or not on a Subaru.

 

[Astro14]

This thread has gone ugly, and personal. Lock time.