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#4584043 - 11/24/17 09:19 PM Oil Filter Effect on Pressure
bunnspecial Online   content


Registered: 11/23/15
Posts: 708
Loc: US
When I bought my MG, it had a Fram Ultra-Guard on it and ran 40-45 psi at warm idle. Since then, out of preference, I've been running a Motorcraft FL-300 and managed the same oil pressure.

I changed the oil today, but opted for the larger FL-1A filter this time around. I'm still using the same oil as what I drained-VR-1 20W-50 but I'm now seeing 65psi at warm idle and the engine will bounce off the oil pressure relief valve(75 psi) at speed.

If anything, I'd expect the larger FL-1A to give me lower pressure than the FL-300. The FL-1A was bought new from the local Ford dealer on Wednesday. The removed FL-300 was bought some time in the fall of 2016.

Has there been some other change in Motorcraft filters that would have led to this?
_________________________
2010 Lincoln MKZ-Mobil 1 5W-30
1970 MG MGB Roadster-Valvoline VR-1 20W-50

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#4584054 - 11/24/17 09:29 PM Re: Oil Filter Effect on Pressure [Re: bunnspecial]
2009Edge Offline


Registered: 06/10/09
Posts: 236
Loc: Texas
Larger filter
more media
more surface area for filtration
lower differential pressure.

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#4584076 - 11/24/17 09:53 PM Re: Oil Filter Effect on Pressure [Re: bunnspecial]
ZeeOSix Offline


Registered: 07/22/10
Posts: 17183
Loc: PNW
An oil filter is not going to effect the idle oil pressure because the positive displacement oil pump is not in pressure relief. Your old oil was probably thinned down and diluted from use, and the new oil was thicker than the old, thereby giving you higher idle oil pressure and also causing the pump to hit pressure relief. Only time oil filter A vs oil filter B (if one was more restrictive than the other) would affect the oil pressure (with sensor after the filter) is at high engine RPM when the oil pump goes in to pressure relief.
_________________________
We Don't Need No Stinkin' Efficiency!

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#4584147 - 11/25/17 02:53 AM Re: Oil Filter Effect on Pressure [Re: bunnspecial]
Johnny2Bad Offline


Registered: 05/20/13
Posts: 1631
Loc: Saskatchewan, Canada
The more restrictive the filter, the lower the Oil Pressure after the filter, and vice versa. Perfectly normal, but it illustrates why OEMs don't use filters with very low size particle entrapment.

This might seem counter-intuitive, but if you place a pressure gauge on each side of a filter you can read the pressure drop directly. Pressure is also related to flow rate; a high flow will lower pressure and vice versa. So it's possible to manage the pressure by manipulating the two (filter beta and oil flow).

Having said all that, it's extremely unusual to have drastic changes in pressure with just a filter change ... fairly large differences in filter restriction have little effect normally. So perhaps your experience is somewhat unusual.
_________________________
'57 FL Straight 50 wt
'90 Miata 1.8L w/Rotrex Supercharger [Mobil1 0W-40]
'96 Ram 1500 [3.7L Mobil1 0W-20 / 1L 15W-50]
'01 PT Cruiser [Mobil1 0W-40]

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#4584166 - 11/25/17 04:55 AM Re: Oil Filter Effect on Pressure [Re: Johnny2Bad]
ZeeOSix Offline


Registered: 07/22/10
Posts: 17183
Loc: PNW
Originally Posted By: Johnny2Bad
The more restrictive the filter, the lower the Oil Pressure after the filter, and vice versa.


Not true with a positive displacement oil pump unless the pump is in pressure relief.

Pump pressure relief usually only happens at high engine RPM when the oil is cold. After the oil is fully hot (200+ F) the pump will typically not hit pressure relief unless a much heavier than specified oil is being used.
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We Don't Need No Stinkin' Efficiency!

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#4584211 - 11/25/17 07:03 AM Re: Oil Filter Effect on Pressure [Re: bunnspecial]
dnewton3 Offline



Registered: 05/14/07
Posts: 7357
Loc: Indianapolis, IN
There is always a little bit of dP across the filter media, but Zee is right; it's minimal for sure. The greatest dP is the lube circuit itself.
See Jim Allen's data from his thread testing dP.
How many times do we have to go over this? (sigh ......)

Consider worst case conditions ...
the dP across media is high, and the filter BP opens. So what?
Seriously, who the heck cares?
If it's common (happens all the time), then where's the proof that this is descrutive? Where are all the dead engines at the side of the road?
Conversely, if this is rare (which data shows it is), then why worry over something that is a minimal event?

Either way, when someone comes forth with credible data directly showing correlation thus linking the dP/BP events to dead engines, I'll give a darn.
Until then, this is typical BITOG hysteria over nothing.




Edited by dnewton3 (11/25/17 07:12 AM)
_________________________
The act of preventative maintenance, in and of itself, is FAR MORE important than brand/grade/base choices among lubes and filters.
- under maintaining something is akin to abuse/neglect; that can kill equipment by shortening the lifespan
- over maintaining something has never been proven to be anything but a waste of time and money

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#4584290 - 11/25/17 08:23 AM Re: Oil Filter Effect on Pressure [Re: bunnspecial]
bullwinkle Offline


Registered: 10/09/04
Posts: 7472
Loc: Cincinnati, OH, USA
I didn't see what weight oil you were using? As mentioned above, likely your old oil was fuel diluted somewhat, maybe sheared, causing viscosity loss. My 6.2 diesel GMC is kind of my filter test bed-it gets 10W30 synthetic blend (T5) in winter, whatever 15W40 I have laying around in summer, and it will bounce off the relief (around 70 PSI) on cold starts, if it's cold enough, no matter what's in the crankcase-UNTIL it warms up, or the oil has 3K or more miles-then it won't go above 50 PSI, and it's done the same with whatever filter is on it, from cheap Puro Classics to Fram Ultras.
_________________________
06 Ram 3500 CTD 4X4(FG Venturi), 93 GMC C3500 6.2, 89 F-450 7.3, 98 XJ 4.0(XG8A), 05 xB(XG3600), 15 Transit 3.7, 03 Merc Grand Marquis 4.6 2V(XG2)

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#4584383 - 11/25/17 10:38 AM Re: Oil Filter Effect on Pressure [Re: bunnspecial]
bunnspecial Online   content


Registered: 11/23/15
Posts: 708
Loc: US
As I said in the opening post, the oil is VR-1 20W-50.

I have NEVER seen pressure this high in this engine, even with a fresh change.
_________________________
2010 Lincoln MKZ-Mobil 1 5W-30
1970 MG MGB Roadster-Valvoline VR-1 20W-50

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#4584446 - 11/25/17 12:06 PM Re: Oil Filter Effect on Pressure [Re: dnewton3]
Linctex Online   content


Registered: 12/31/16
Posts: 5692
Loc: Waco, TX
Originally Posted By: dnewton3

See Jim Allen's data from his thread testing dP.
How many times do we have to go over this? (sigh ......)


https://bobistheoilguy.com/forums/ubbthreads.php/topics/3197094
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"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."

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#4584478 - 11/25/17 12:49 PM Re: Oil Filter Effect on Pressure [Re: bunnspecial]
ZeeOSix Offline


Registered: 07/22/10
Posts: 17183
Loc: PNW
Originally Posted By: bunnspecial
When I bought my MG ...

Do you know for sure if the oil pressure sensor is located before or after the filter?

If the sensor is located before the filter, then you would see the oil pressure change due to the filter's flow restriction.

If the sensor is located after the filter then the oil pressure will not be affected by the filter unless the positive displacement oil pump is in pressure relief, which happens rarely as mentioned earlier - ie, very thick oil and high engine RPM.
_________________________
We Don't Need No Stinkin' Efficiency!

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#4584516 - 11/25/17 01:30 PM Re: Oil Filter Effect on Pressure [Re: ZeeOSix]
bunnspecial Online   content


Registered: 11/23/15
Posts: 708
Loc: US
Originally Posted By: ZeeOSix
Originally Posted By: bunnspecial
When I bought my MG ...

Do you know for sure if the oil pressure sensor is located before or after the filter?

If the sensor is located before the filter, then you would see the oil pressure change due to the filter's flow restriction.

If the sensor is located after the filter then the oil pressure will not be affected by the filter unless the positive displacement oil pump is in pressure relief, which happens rarely as mentioned earlier - ie, very thick oil and high engine RPM.


That honestly is something I should know but don't. The take-off for either the mechanical gauge(62-67, 73-80) or electric gauge sender(68-72) is located right next to the rear oil cooler take off. That is located just BEHIND the distributor, which should be just in line with the oil pump out.

I have a block in the storage building that I'm planning on having machined this winter so I can start assembling it for my MGA. I'll try to look at it and see if I can figure it out if I can't find the answer elsewhere.
_________________________
2010 Lincoln MKZ-Mobil 1 5W-30
1970 MG MGB Roadster-Valvoline VR-1 20W-50

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