Amsoil pressure drop after 3,500 miles

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Great discovery Overkill! I like it when I am impressed. (y)

Since you only have about 3K on your current OCI and it has "stopped up" the filter, you may want to
shorten your OCI to 3K the next few changes. I probably wouldn't go 5K right yet.

Hopefully you can find a real GM filter and use it with the Amsoil. Sorta expensive but it
seems like it is doing a great job cleaning.

Awfully nice for Amsoil to refund your money.
 
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2014 Tahoe with 9.6:1 compression when new. Yep, peak performance with regular unleaded gasoline. Cannot even tell us what he pays for his glorious E85 fill up fuel?:eek:
Static compression is not dynamic cylinder pressure. An advanced intake event at moderate RPM can create huge cylinder pressures.
Most modern engines will produce more power with fuel with a higher AKI.

We don't have E85 here, but you should experience less problems with phase separation than with E10 or E15
Me, I'm happier with E0. To bad it's at the Airport
 
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^^^^^^^^^^^^^^^^^^^^^^^^

This is a great post in my opinion. One of the examples why Overkill is one of the best members on here. A post that is detailed, informative and articulated extremely well.
But, 'The Beatle's Hater' pulled a Norm Crosby with exasperate instead of exacerbate :)
Then, there was that quite arguable oil pressure theorem.

I don't know ... these social media partial truths have come home to roost! :)
 

OVERKILL

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Only if the pump is in relief. If the flow volume doesn't change, then the pressure won't change if the oil temp/viscosity is constant.

If the oil pressure sensor was before the filter, then you would see the pressure increase if the filter was clogging and the pump wasn't in relief.

Per yourself:
ZeeOSix said:
Most vehicles have the oil pressure sensor located after the oil filter, so the slight pressure drop across the oil filter (along with the oil gallery length between the pump and the pressure sensor) will make the pressure at the sensor slightly lower than the pressure right at the pump outlet.

I recall from Gary's testing, this amount was VERY slight, only 1 or 2 psi with a filter that was in good shape.

In the context of this thread however, we are talking about a filter that's potentially fully loaded up to the point that it's a "bigger" resister than the engine. A properly functioning filter that isn't in that state of course will pose much less resistance than the engine and thus be essentially transparent.

Per your last bit, we are talking about the same thing. If he was measuring pressure before the filter, we'd see it elevated because of the condition of the filter. We are just seeing the artifact of that on the far side. I would assume this is compounded by cold, thick oil.

This old quote from Gary Allan sums it up nicely:
Gary Allen said:
If you can agree that pump output is not substantially effected below the relief level ..then 100% of the sensible pump output goes to the engine. That means that regardless of visc/flow rate/whatever ..the "produced back pressure" will be identical as viewed on the engine side of the media. Any "added" pressure being contributed by the media HAS to fall into a subordinate relationship to the VASTLY GREATER resistance that the engine downstream creates. Outside of the minor pump losses ..this is a series circuit as viewed by the pump and filter ..any complexity to it beyond the oil gallery is irrelevant. The whole engine is one BIG resistance/restriction and generates the most back pressure at the given flow. The filter has to fall into a proportion of that massive restriction ..commensurate with how it elevates the pressure in addition to the engine. Loading (contamination) can surely effect PSID in a "reactive" manner that falls outside of a static "vacuum" (linear) view. It's mostly transient in nature ...but for the most part you're looking at the long end of a long curve in a filter's life. There's no two ways about it ..a filter has both a resistance and an impedence to flow. But when you're not in pump relief ..or don't have a worn leaky pump or one of low efficiency (remember- we're talking the vast majority of users and aren't accounting for every "what if" here) ..it's TRUMPED so big time by the engine in "relative resistance" ...making it a very small player in pressure influence.

In the scenario I'm envisioning with the OP, that filter is fully loaded to the point that the media bypass is open during operation, necessitating whatever drop across the media is required to achieve that, making the media higher resistance than the engine beyond it.

BTW, I just found one of the old threads where you, Doug, myself and Gary got "into it" on this subject. Gary was calling you SuperBusa, it was a good time, lol 😁
 
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Looks like we need a combi gauge with Pre and post filter oil pressures;
I would sure have liked one on my problematic Nissan and Toyota.

At Idle, the pump should not be bypassing and it would ramp up pre filter pressure as it maintains volume flow at x rpm.
Bypassed in the filter button or not, that oil volume is going into the engine. There may be some minor losses in the pump.

But we don't know if the pump is bypassing at idle or near idle: that would be problematic. I would think not.
-Ken
 
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The 3rd Gen LS engines have a FIXED pressure oil pump, which tends to be on the low side, since the OPS is up on the back of the engine, after the filter & galleries. The oil pickup AND pump output both go through the lip of the oil pan, which can also leak. I've had intermittent low oil pressure symptoms with the LQ4 6.0 LS in the '11 Express in my sig, which Hertz likely didn't use Dexos rated oil in (just a guess), but still running out the OLM as if it did (the guy I bought it from did the same with Jiffy Lube dino). In my case, the ACDelco UPF filter actually increased oil pressure with the same fairly new RGT 5W30 I used with an Ultra. I actually bought a Melling HV oil pump & pickup kit for it, I'm sure replacing it & the oil pan gasket & pickup are in my future...
 
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Looks like we need a combi gauge with Pre and post filter oil pressures;
I would sure have liked one on my problematic Nissan and Toyota.

At Idle, the pump should not be bypassing and it would ramp up pre filter pressure as it maintains volume flow at x rpm.
Bypassed in the filter button or not, that oil volume is going into the engine. There may be some minor losses in the pump.

But we don't know if the pump is bypassing at idle or near idle: that would be problematic. I would think not.
-Ken
There's a lot of potential factors with oil pressure in an LS engine, apparently-everything from clogged pickup, worn oil pump, leaking oring seal in pan lip, worn bearings, fuel in oil, etc. etc. I doubt if the OP plugged an Amsoil filter in 3K, unless he has a major sludge monster! Awaiting filter dissection!
 
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Complete and total nonsense that the engine is high compression. Complete and total nonsense that such a relatively low compression NA engine is making anywhere near that power on 85% ethanol 15% gasoline.
 

Circuit Rider

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Complete and total nonsense that the engine is high compression. Complete and total nonsense that such a relatively low compression NA engine is making anywhere near that power on 85% ethanol 15% gasoline.
I think you’re misunderstanding the difference between compression and compression ratio.

For one, you noted “when new”. Compression RATIO doesn’t change with wear. Compression ratio is the difference in volume in the cylinder between the piston being at the top and at the bottom of the stroke. There is 10x more physical “space” inside a cylinder at the bottom of the stroke than the top in a 10:1 compression ratio. You don’t measure compression ratio with a compression gauge.

Wear can allow some of that air to escape past rings or perhaps valves and that will result in lower compression, but it doesn’t change the compression ratio of the engine.

Back in the 1960’s, every engine was basically the same so displacement and compression ratio told you everything you needed to know about an engine. Then you could say things like “You need X fuel at Y compression ratio”. Again, in the example of my Ford Focus with a 12.5:1 compression ratio; such an engine would blow up with 87 octane fuel. But because of it’s variable valve timing (the same technology which is present in the 5.3) and more advanced intake and ignition systems, it’s able to operate on 87 without any knocking.

The whole concept behind forced induction is ramming more air inside a cylinder and it’s often done with a lower compression ratio. It’s usually more efficient to have a low compression ratio engine with a lot of boost than a high compression ratio with a little boost.

It sounds like you aren’t very familiar with E85 and the impact that higher octane fuels can have on modern engines. I shared the link you asked me to share; but there are also a lot of other resources out there. Not every flex fuel engine takes advantage of E85 (some run like absolute garbage with E85). Traditionally the ones that benefit the most are turbocharged engines because the high octane rating means they can cram tons and tons of air into the cylinder without pre-igniting the fuel and causing damage. Even though my 5.3 isn’t turbocharged, it can still vary the amount of air in the cylinder using a variable valve timing system; which means it has more air in it when running E85 (it detects the fuel using an alcohol sensor), thus, more power. If that same amount of air were present with 87 or even 93 octane regular gasoline, detonation could occur. Because; while the RATIO (change in volume) would be the same, the heat and pressure would be much higher when more air is allowed into the cylinder when the piston is at the bottom of the stroke.

Another way to look at it might be to consider that the engine is designed to run on E85 but is capable of de-tuning itself to run regular gasoline safely without damage; instead of trying to wrap your head around an engine adjusting to take advantage of E85. If you could buy 105 octane gasoline, you’d make even MORE power.

I think most of the confusion is because there are two different components at play here. BTU and AKI. E85 has a lower BTU rating than pure gasoline, meaning less energy in a quantity of the fuel. (Hence, the poorer fuel economy). If that was the only difference, then power with E85 would be reduced commensurate to that drop in BTU. However, the second factor is AKI (anti-knock index). E85 has an AKI of roughly 105, compared to 87-93 typically available in gas stations. If an engine can take advantage of a high AKI, it can OVERCOME the low BTU’s and even leap frog it to make more power.
 

Circuit Rider

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I am more than a little shocked they didn’t want the oil filter back.
Well, I have bad news.

They reached out today and want the filter back. Had I not checked my e-mail, I was going to open it up while I was home for lunch today. But; alas, I did before I left the office and obliged. So I’m sending them the filter back.

Hopefully y’all don’t hate me too much for that. I’ll definitely cut open the second filter when it’s time to replace it and post pics.
 

ZeeOSix

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Well, I have bad news.

They reached out today and want the filter back. Had I not checked my e-mail, I was going to open it up while I was home for lunch today. But; alas, I did before I left the office and obliged. So I’m sending them the filter back.

Hopefully y’all don’t hate me too much for that. I’ll definitely cut open the second filter when it’s time to replace it and post pics.
Ask them if they could bench test it for flow resistance and determine if it was in bypass at a low flow rate with 10 cSt oil viscosity.
 

ZeeOSix

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Per yourself:
1) Only if the pump is in relief. If the flow volume doesn't change, then the pressure won't change if the oil temp/viscosity is constant.
If the oil pressure sensor was before the filter, then you would see the pressure increase if the filter was clogging and the pump wasn't in relief.

and

2) Most vehicles have the oil pressure sensor located after the oil filter, so the slight pressure drop across the oil filter (along with the oil gallery length between the pump and the pressure sensor) will make the pressure at the sensor slightly lower than the pressure right at the pump outlet.
^^^ Both of those things hold true in a healthy engine using a non-variable PD pump that is also healthy. The oil pressure at any point in the engine is basically an indirect measurement of the oil viscosity and oil flow conditions happening at that exact physical point in the oiling system. Engine designers typically put the oil pressure sensor in a big main oil gallery after the oil filter. If the sensor is located way down stream but still in the main gallery (like in this engine), then there could be a PSI or two of pressure drop from the filter to the sensor - that's what my comment 2) above is talking about.

But if you look at the oil pressure right at the location of the sensor it still is giving a flow and viscosity condition reading. So if the flow volume and oil viscosity is constant at that location, then so is the pressure. And if an oil filter becomes loaded up, the PD pump (if healthy) will increase its output pressure in order to maintain the same output volume while at the same RPM. If the same volume is still flowing (with viscosity constant), then the pressure at the sensor after the filter will also stay the same. Only if the PD pump goes into pressure relief (and/or starts slipping and becoming less efficient at pumping) is when the volume going to the filter and engine will be cut back, and that is when the pressure at the sensor will also be cut back. This is all with a healthy oiling system and oil pump. If other things are going on with the oiling system (inlet screen, pump pick-up O-ring) or pump (worn pump, relief not working correctly), then things may behave differently.

There have been a few similar threads in the Oil Filter forum on this same GM engine I believe with the same symptoms - seems to be a common issue. They all had high mileage IIRC. From all those discussions, it was never really very clear what the cause was. IMO, I think there are more factors involved beside just a loaded up oil filter. But a loaded up oil filter may cause lower oil pressure much easier in an engine with a worn oil pump or other oiling system issues.

I recall from Gary's testing, this amount was VERY slight, only 1 or 2 psi with a filter that was in good shape.
Yes, a new filter will have a pretty low PSID across the filter with hot oil (low viscosity) and low flow rate (engine at idle or low RPM).

In the context of this thread however, we are talking about a filter that's potentially fully loaded up to the point that it's a "bigger" resister than the engine. A properly functioning filter that isn't in that state of course will pose much less resistance than the engine and thus be essentially transparent.
Yes, a totally clogged oil filter would still open up its bypass valve, but the flow going through the typically small bypass valve would most likely put the pump in relief, and at a very low RPM.

Typically, a new oil filter only makes up around 1/15th the resistance as the whole engine - it's typically "transparent" to the oiling system as the saying goes. At an engine inlet oil pressure of say 80 PSI (call it the pump relief setting) and the PSID across the filter would typically be around 5 PSI. If a totally clogged oil filter was a bigger resistor to flow then the engine, then oil pump would be in relief at a very low RPM and the oil pressure very low at a low RPM. If the pump was in total pressure relief, then the oil pressure would also be pretty low at higher RPM too - maybe even lower than what the OP saw.

In the scenario I'm envisioning with the OP, that filter is fully loaded to the point that the media bypass is open during operation, necessitating whatever drop across the media is required to achieve that, making the media higher resistance than the engine beyond it.
If the filter was near or at 100% clogged, the filter bypass would be wide open and the pump most likely also be in pressure relief. Also, if the only major flow path through the filter was the small bypass valve opening, then that adds flow resistance, which would cause the pump to hit relief even sooner and thereby cutting flow and oil pressure at the sensor. And who knows how healthy the oil pump is because it's also possible that when the pump is at pressure relief it might also becoming less efficient at pumping oil due to more "slip". That would show up more with hot thin oil vs cold thick oil of course.
 
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OVERKILL

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If the filter was near or at 100% clogged, the filter bypass would be wide open and the pump most likely also be in pressure relief. Also, if the only major flow path through the filter was the small bypass valve opening, then that adds flow resistance, which would cause the pump to hit relief even sooner and thereby cutting flow and oil pressure at the sensor. And who knows how healthy the oil pump is because it's also possible that when the pump is at pressure relief it might also becoming less efficient at pumping oil due to more "slip". That would show up more with hot thin oil vs cold thick oil of course.
That's going to depend on the size of the bypass for the filter.

The LSx family, like the venerable SBC, has the media bypass in the block, and it's pretty large. You can see that relative to the engine feed here:
CBW-072-3__95685.1507731959.jpg


My theory is/was that the media is so clogged that it's producing a significant differential. It may be opening the in-block bypass, which, IIRC, is around 10psi? which is pretty consistent with the pressure drop he's observing, but you are right in that there may be more to this. Would love to see the filter internals, but that doesn't sound like it is in the cards, so hopefully AMSOIL provides us with something useful :)
 
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ZeeOSix

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That's going to depend on the size of the bypass for the filter.

The LSx family, like the venerable SBC, has the media bypass in the block, and it's pretty large. You can see that relative to the engine feed here:
CBW-072-3__95685.1507731959.jpg


My theory is/was that the media is so clogged that it's producing a significant differential. It may be opening the in-block bypass, which, IIRC, is around 10psi? which is pretty consistent with the pressure drop he's observing, but you are right in that there may be more to this. Would love to see the filter internals, but that doesn't sound like it is in the cards, so hopefully AMSOIL provides us with something useful :)
Yes, but I think the OPs truck is new enough where GM got rid of the in-block filter bypass. In that case the bypass valve flow area in the filter is probably less than in an in-block bypass valve ... which would make a very clogged filter more apparent if the filter is mainly in bypass flow instead of through the media flow. That small filter bypass flow area could also make the oil pump hit bypass sooner than later too.
 
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Circuit Rider

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Yes, but I think the OPs truck is new enough where GM got rid of the in-block filter bypass. In that case the bypass valve flow area in the filter is probably less than in an in-block bypass valve ... which would make a very clogged filter more apparent if the filter is mainly in bypass flow instead of through the media flow.
This is my first GM product in quite a long time and my first V8 GM product.

I’m learning that it’s kind of a pain to have something with an engine that was produced for such a long time and has so many different (but only SLIGHTLY different) variations and versions.
 

OVERKILL

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Yes, but I think the OPs truck is new enough where GM got rid of the in-block filter bypass. In that case the bypass valve flow area in the filter is probably less than in an in-block bypass valve ... which would make a very clogged filter more apparent if the filter is mainly in bypass flow instead of through the media flow. That small filter bypass flow area could also make the oil pump hit bypass sooner than later too.

I'm not up to speed on my GM stuff enough to know if that's the case or not unfortunately.
 
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I was going to suggest changing out the filter but too late for that. I see this a lot where someone purchases a used vehicle with unknown service history especially when going to a synthetic oil that it cleans a lot of the crud out of there and it all has to end up somewhere and luckily for you it was the oil filter and caught it in time before it could really do any damage.

Typically when I purchase a used vehicle and don't know the history I'll check the oil to see if it's been changed recently or not but when I do change it I mostly use Chevron Delo xle 10w30 which is a great oil and cheap too but if needs 0w20 or 5w20 then I'd use a good quality synthetic blend and monitor the oil consumption and change it out between 3k-5k miles. I'm usually not picky about filters but do tend to stay away from those orange cans but will use their other ones but I usually go with the oem filters such as AC Delco, Motorcraft, & Honda but also use Napa/Wix & Purolator.
 
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