Pressure drop when using pennzoil full synthetic
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Originally Posted by kstanf150
I think your right ðŸ™
No he is here.
I think your right ðŸ™
No he is here.
Originally Posted by Tyler13
Oil change at Firestone using Pennzoil full synthetic 5w30, idle oil pressure 18
2000 rpm 38
Oil change at Goodyear with Valvoline full synthetic 5w30, idle oil pressure 38
2000 rpm 58
This has happened twice. Valvoline maintained that oil pressure for the duration of use roughly 6000 miles all highway. Would get slight lifter noise also using Pennzoil at idle. No lifter noise with Valvoline. 2003 5.3 avalanche high mileage. What gives with the Pennzoil?
You learned BITOG's No. 1 rule the hard way: Never insult anyone's oil.
That said, it's not the Pennzoil that's causing the problem if there is any problem. We are talking about premium oils here, let alone any API-certified oil, even a very cheap one, which should also be fine.
I don't know which oil pressure is correct for this car, whether the low one or the high one.
One thing I noticed is that the recommended oil filter for this car doesn't have a bypass valve, which will cause high oil pressure if the oil filter is clogged. Conversely, if you install an oil filter with a bypass valve, when the oil filter gets clogged, you will have lower oil pressure.
This table is for my car but you can also troubleshoot yours with it. It's definitely not the "engine oil poor quality." It's one of the other causes in the table. Again, I don't know whether the problem here is low oil pressure or high oil pressure.
![[Linked Image]](https://lh3.googleusercontent.com/YroJ8GgHe2yQ52olpiRe9UtlfCjn-sKsfD-EQlvxX8xU-pla287wPeTkD2DxcPMe3Ka6xtpLUaRVyvhrNEOO_nQzdztV2bBJzHTwxxocN1H6yqf_V7id7T5QOWBtRXlK8EHAwiaq8OoaqTNEHyRgUj5EP2x53JMMm_gUG0nEd9Vn4sVi2tIn5i3Hzg4E_anjXEZjLfomS0rVnb1K2DDyJzawYfQ4Wu0DNktv22leN6XuEaPAhZSfgX8cX3PI8C6cxpVvVFO07CzTsiZu2BnVxx1Qh8fAU3wutnsaVeRoTT0cP3h9A_6X2xFCwYNYREnsbomeHrgNwhp-nY7J82GT46zGPph58nKhPvb1A-L-btaVsvDNDV3_aSTxsvjMLq0r3dPkaF4YxUJFcEe9nq1rzdG_DGU0oFKUbjyWf3ys4u0NGCtkT--hyci6fePZYuan1_EdivbSxYahMAkNMG4kl22d9WgiOGoTOEvwMTgYF7Q4aFaoE08p7-CMk8ntBt_A0f3iPAtrIUpVfX7UM-bvA6FK4wiQqllTnDI4mjOFluigHs5f100WZJ3147L-cy-zQt3g1sMxE0OUNsHMQ6DohUO5dP3SxzHqIC3L8c8cACWC6-kFjjQ6owuJbR-50GEYVEiVTDOFdYUphadGbB4f3icVtTikZHVv=w1200-no?.png "[Linked Image]")
Oil change at Firestone using Pennzoil full synthetic 5w30, idle oil pressure 18
2000 rpm 38
Oil change at Goodyear with Valvoline full synthetic 5w30, idle oil pressure 38
2000 rpm 58
This has happened twice. Valvoline maintained that oil pressure for the duration of use roughly 6000 miles all highway. Would get slight lifter noise also using Pennzoil at idle. No lifter noise with Valvoline. 2003 5.3 avalanche high mileage. What gives with the Pennzoil?
You learned BITOG's No. 1 rule the hard way: Never insult anyone's oil.
That said, it's not the Pennzoil that's causing the problem if there is any problem. We are talking about premium oils here, let alone any API-certified oil, even a very cheap one, which should also be fine.
I don't know which oil pressure is correct for this car, whether the low one or the high one.
One thing I noticed is that the recommended oil filter for this car doesn't have a bypass valve, which will cause high oil pressure if the oil filter is clogged. Conversely, if you install an oil filter with a bypass valve, when the oil filter gets clogged, you will have lower oil pressure.
This table is for my car but you can also troubleshoot yours with it. It's definitely not the "engine oil poor quality." It's one of the other causes in the table. Again, I don't know whether the problem here is low oil pressure or high oil pressure.
Agreed; two 5w-30 ILSAC/dexos1 type oils are about as similar as can be, particularly viscometrically.
I suggest the OP really doesnt know what oil he is using.
Since the oil is being changed in commercial repair shops, how can he be sure what weight oil is being used?
Either way, something is out of whack and think I would skip going to the shop with the crazy high oil pressure and/or as a baseline, go to a 3rd oil change place and see the results.
Since the oil is being changed in commercial repair shops, how can he be sure what weight oil is being used?
Either way, something is out of whack and think I would skip going to the shop with the crazy high oil pressure and/or as a baseline, go to a 3rd oil change place and see the results.
Last edited:
I think this is the answer OP was looking for:
"Pennzoil BAD"
"Pennzoil BAD"
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Originally Posted by alarmguy
Since the oil is being changed in commercial repair shops, how can he be sure what weight oil is being used?
I definitely agree with this one. There's no telling what kind've cheap bulk stuff they're using.
Since the oil is being changed in commercial repair shops, how can he be sure what weight oil is being used?
I definitely agree with this one. There's no telling what kind've cheap bulk stuff they're using.
Originally Posted by ZeeOSix
Originally Posted by MrMoody
Originally Posted by ZeeOSix
A positive displacement oil pump is going to force the same oil flow volume through any filter at idle.
Even if this was true, much less on a worn pump, the pressure is measured after the filter, and different filters can have different delta-p at the same flow and viscosity. Not that it should be much on a new filter with hot oil.
You missed the point. With a positive displacement oil pump (assume it's healthy) the same flow will be at the pressure sensor (especially at idle RPM) regardless of the filter's flow restriction. The only thing that happens with a more flow restrictive filter is the delta-p across the filter increases with the same flow. If the flow is the same coming out the filter at the point of the pressure sensor (ie, because of the positive displacement oil pump), then there will be no loss in measured oil pressure because of oil filter restriction.
Z- Are the following assumptions incorrect?
If the pump has a relief bypass - as many do employ - you do not have a positive displacement "system" in all instances. With moderate or greater Delta P around the filter, the pump will ramp up pressure to the bypass point , say 55 psi, then bypass to maintain that. Whatever pressure is post filter will reveal the Delta P If the pump bypass is malfunctioning due to varnish or foreign material - which it likely could be - you can have low or extreme system pressure situations at the filter.
Thanks - Ken
Originally Posted by MrMoody
Originally Posted by ZeeOSix
A positive displacement oil pump is going to force the same oil flow volume through any filter at idle.
Even if this was true, much less on a worn pump, the pressure is measured after the filter, and different filters can have different delta-p at the same flow and viscosity. Not that it should be much on a new filter with hot oil.
You missed the point. With a positive displacement oil pump (assume it's healthy) the same flow will be at the pressure sensor (especially at idle RPM) regardless of the filter's flow restriction. The only thing that happens with a more flow restrictive filter is the delta-p across the filter increases with the same flow. If the flow is the same coming out the filter at the point of the pressure sensor (ie, because of the positive displacement oil pump), then there will be no loss in measured oil pressure because of oil filter restriction.
Z- Are the following assumptions incorrect?
If the pump has a relief bypass - as many do employ - you do not have a positive displacement "system" in all instances. With moderate or greater Delta P around the filter, the pump will ramp up pressure to the bypass point , say 55 psi, then bypass to maintain that. Whatever pressure is post filter will reveal the Delta P If the pump bypass is malfunctioning due to varnish or foreign material - which it likely could be - you can have low or extreme system pressure situations at the filter.
Thanks - Ken
There are at least two variables here, and it will be hard to figure it out without eliminating one of them.
Both oils mentioned are good quality. They may differ in some ways, but either should protect your engine.
You need to run the current oil with the current filter for 1K or 2K miles, keep the oil and change the filter to Fram Ultra, (I chose the Fram only because I like it). Run the oil for the rest of the oci with this alternative filter.
Go go the other place and get oil and filter changed. Run that oil and filter for 1K or 2K miles, then change only the filter. Use the same kind of alternative filter as before.
Record your observations with all scenarios and report back here.
There are some genius level people on here, (I am not one of them), and they will help you diagnose your problem. They just need more info.
I'm sure the test I prescribed can be improved greatly by someone who actually knows what they are doing. Please feel free to edit.
Both oils mentioned are good quality. They may differ in some ways, but either should protect your engine.
You need to run the current oil with the current filter for 1K or 2K miles, keep the oil and change the filter to Fram Ultra, (I chose the Fram only because I like it). Run the oil for the rest of the oci with this alternative filter.
Go go the other place and get oil and filter changed. Run that oil and filter for 1K or 2K miles, then change only the filter. Use the same kind of alternative filter as before.
Record your observations with all scenarios and report back here.
There are some genius level people on here, (I am not one of them), and they will help you diagnose your problem. They just need more info.
I'm sure the test I prescribed can be improved greatly by someone who actually knows what they are doing. Please feel free to edit.
gathermewool
Site Donor 2023
For those who missed it or who can't be bothered to read more than three sentences before bailing on a "TL;DR" post...
Originally Posted by Tyler13
This is repeatable. The oil was just changed from Valvoline with over 6000 miles less than 100 miles ago. Will be dumping that for Valvoline which will be the 3rd time. This truck runs straight through on highway from CT. to Cape Breton Island a distance if 900 miles each way straight thru stopping only for gas and food. This is done seven or eight times a year. For further info, over the past several years Kendall full synthetic has maintained the higher pressure as has the Valvoline. On the down side Mobil 1 falls into the low pressure with Pennzoil. If it's not something relating to the oil itself it doesn't make sense. I have done the Kendall and Mobil 1 myself so there was no switching going on here. The pressure ALWAYS returns to normal, the higher pressure, when it is replaced with Valvoline or Kendall. Didn't think I would have to get this far into this to explain. A slight drop I could understand with the possible difference in viscocity, but 20 lbs seems a bit much.
Originally Posted by Tyler13
This is repeatable. The oil was just changed from Valvoline with over 6000 miles less than 100 miles ago. Will be dumping that for Valvoline which will be the 3rd time. This truck runs straight through on highway from CT. to Cape Breton Island a distance if 900 miles each way straight thru stopping only for gas and food. This is done seven or eight times a year. For further info, over the past several years Kendall full synthetic has maintained the higher pressure as has the Valvoline. On the down side Mobil 1 falls into the low pressure with Pennzoil. If it's not something relating to the oil itself it doesn't make sense. I have done the Kendall and Mobil 1 myself so there was no switching going on here. The pressure ALWAYS returns to normal, the higher pressure, when it is replaced with Valvoline or Kendall. Didn't think I would have to get this far into this to explain. A slight drop I could understand with the possible difference in viscocity, but 20 lbs seems a bit much.
Originally Posted by Tyler13
This is repeatable. The oil was just changed from Valvoline with over 6000 miles less than 100 miles ago. Will be dumping that for Valvoline which will be the 3rd time. This truck runs straight through on highway from CT. to Cape Breton Island a distance if 900 miles each way straight thru stopping only for gas and food. This is done seven or eight times a year. For further info, over the past several years Kendall full synthetic has maintained the higher pressure as has the Valvoline. On the down side Mobil 1 falls into the low pressure with Pennzoil. If it's not something relating to the oil itself it doesn't make sense. I have done the Kendall and Mobil 1 myself so there was no switching going on here. The pressure ALWAYS returns to normal, the higher pressure, when it is replaced with Valvoline or Kendall. Didn't think I would have to get this far into this to explain. A slight drop I could understand with the possible difference in viscocity, but 20 lbs seems a bit much.
Oil pressure depends on the HTHSV:
PPPP 5W-30 HTHSV = 3.0 cP
M1 5W-30 HTHSV = 3.1 cP
Kendall dexos1 Gen 2 5W-30 HTHSV = 3.2 cP
VAS 5W-30 HTHSV = 3.2 cP
Kendall dexos1 Gen 2 and VAS are indeed the thickest ILSAC 5W-30 oils you can get.
However, the oil pressure difference should be less than about 10% according to these HTHSV values in a healthy engine. (The reported HTHSV is measured at 150 C -- you need to look at the HTHSV at a somewhat smaller temperature to know the exact dynamic viscosity in the bearings.) Nevertheless, if your bearing clearances are beyond acceptable wear, a small drop in the viscosity can result in a big drop in the oil pressure, as there would be too much bearing side leakage, which would put more constraint on the minimum viscosity required to maintain normal oil pressure.
If you are using the same oil filter in each case (no bypass valve), the only explanation is that either your bearings or your oil pump are at the point of failing.
You might want to go with a Euro 5W-30, such as the Kendall GT-1 Euro+ ACEA C3, which has HTHSV = 3.6 cP. This will help with your what seems to be a failing high-mileage engine.
A UOA may give you a clue on whether your bearings are wearing away to failure.
This is repeatable. The oil was just changed from Valvoline with over 6000 miles less than 100 miles ago. Will be dumping that for Valvoline which will be the 3rd time. This truck runs straight through on highway from CT. to Cape Breton Island a distance if 900 miles each way straight thru stopping only for gas and food. This is done seven or eight times a year. For further info, over the past several years Kendall full synthetic has maintained the higher pressure as has the Valvoline. On the down side Mobil 1 falls into the low pressure with Pennzoil. If it's not something relating to the oil itself it doesn't make sense. I have done the Kendall and Mobil 1 myself so there was no switching going on here. The pressure ALWAYS returns to normal, the higher pressure, when it is replaced with Valvoline or Kendall. Didn't think I would have to get this far into this to explain. A slight drop I could understand with the possible difference in viscocity, but 20 lbs seems a bit much.
Oil pressure depends on the HTHSV:
PPPP 5W-30 HTHSV = 3.0 cP
M1 5W-30 HTHSV = 3.1 cP
Kendall dexos1 Gen 2 5W-30 HTHSV = 3.2 cP
VAS 5W-30 HTHSV = 3.2 cP
Kendall dexos1 Gen 2 and VAS are indeed the thickest ILSAC 5W-30 oils you can get.
However, the oil pressure difference should be less than about 10% according to these HTHSV values in a healthy engine. (The reported HTHSV is measured at 150 C -- you need to look at the HTHSV at a somewhat smaller temperature to know the exact dynamic viscosity in the bearings.) Nevertheless, if your bearing clearances are beyond acceptable wear, a small drop in the viscosity can result in a big drop in the oil pressure, as there would be too much bearing side leakage, which would put more constraint on the minimum viscosity required to maintain normal oil pressure.
If you are using the same oil filter in each case (no bypass valve), the only explanation is that either your bearings or your oil pump are at the point of failing.
You might want to go with a Euro 5W-30, such as the Kendall GT-1 Euro+ ACEA C3, which has HTHSV = 3.6 cP. This will help with your what seems to be a failing high-mileage engine.
A UOA may give you a clue on whether your bearings are wearing away to failure.
Originally Posted by ARCOgraphite
Originally Posted by ZeeOSix
Originally Posted by MrMoody
Originally Posted by ZeeOSix
A positive displacement oil pump is going to force the same oil flow volume through any filter at idle.
Even if this was true, much less on a worn pump, the pressure is measured after the filter, and different filters can have different delta-p at the same flow and viscosity. Not that it should be much on a new filter with hot oil.
You missed the point. With a positive displacement oil pump (assume it's healthy) the same flow will be at the pressure sensor (especially at idle RPM) regardless of the filter's flow restriction. The only thing that happens with a more flow restrictive filter is the delta-p across the filter increases with the same flow. If the flow is the same coming out the filter at the point of the pressure sensor (ie, because of the positive displacement oil pump), then there will be no loss in measured oil pressure because of oil filter restriction.
Z- Are the following assumptions incorrect?
If the pump has a relief bypass - as many do employ - you do not have a positive displacement "system" in all instances. With moderate or greater Delta P around the filter, the pump will ramp up pressure to the bypass point , say 55 psi, then bypass to maintain that. Whatever pressure is post filter will reveal the Delta P If the pump bypass is malfunctioning due to varnish or foreign material - which it likely could be - you can have low or extreme system pressure situations at the filter.
Thanks - Ken
As long as the oil pump is NOT in pressure relief, then all the oil coming out the pump will be forced through the oil filter and the engine's oiling system. That is regardless of what the delta-p is across the oil filter. The filter bypass valve and the pump pressure relief valve operate independently - ie, they are not dependent on each other. The only time the oil flow will be reduces going through the filter/engine is when the pump hit's pressure relief. Yes, a sticky pump relief valve can cause low oil pressure too if it's stuck partially open for some reason.
But as I mentioned, I HIGHLY doubt the pump is in pressure relief with hot oil and engine idle RPM conditions. The only way that could happen is if the filter was totally clogged and the bypass valve in the filter was super small flow area. Actually, in this case the filter bypass valve is in the block (typical older GM design). Doubt that's what is going on.
What the OP need to do is change JUST the oil and leave whatever filter is on the engine to see if just changing oil is causing the oil pressure difference.
Originally Posted by ZeeOSix
Originally Posted by MrMoody
Originally Posted by ZeeOSix
A positive displacement oil pump is going to force the same oil flow volume through any filter at idle.
Even if this was true, much less on a worn pump, the pressure is measured after the filter, and different filters can have different delta-p at the same flow and viscosity. Not that it should be much on a new filter with hot oil.
You missed the point. With a positive displacement oil pump (assume it's healthy) the same flow will be at the pressure sensor (especially at idle RPM) regardless of the filter's flow restriction. The only thing that happens with a more flow restrictive filter is the delta-p across the filter increases with the same flow. If the flow is the same coming out the filter at the point of the pressure sensor (ie, because of the positive displacement oil pump), then there will be no loss in measured oil pressure because of oil filter restriction.
Z- Are the following assumptions incorrect?
If the pump has a relief bypass - as many do employ - you do not have a positive displacement "system" in all instances. With moderate or greater Delta P around the filter, the pump will ramp up pressure to the bypass point , say 55 psi, then bypass to maintain that. Whatever pressure is post filter will reveal the Delta P If the pump bypass is malfunctioning due to varnish or foreign material - which it likely could be - you can have low or extreme system pressure situations at the filter.
Thanks - Ken
As long as the oil pump is NOT in pressure relief, then all the oil coming out the pump will be forced through the oil filter and the engine's oiling system. That is regardless of what the delta-p is across the oil filter. The filter bypass valve and the pump pressure relief valve operate independently - ie, they are not dependent on each other. The only time the oil flow will be reduces going through the filter/engine is when the pump hit's pressure relief. Yes, a sticky pump relief valve can cause low oil pressure too if it's stuck partially open for some reason.
But as I mentioned, I HIGHLY doubt the pump is in pressure relief with hot oil and engine idle RPM conditions. The only way that could happen is if the filter was totally clogged and the bypass valve in the filter was super small flow area. Actually, in this case the filter bypass valve is in the block (typical older GM design). Doubt that's what is going on.
What the OP need to do is change JUST the oil and leave whatever filter is on the engine to see if just changing oil is causing the oil pressure difference.
Originally Posted by Gokhan
One thing I noticed is that the recommended oil filter for this car doesn't have a bypass valve, which will cause high oil pressure if the oil filter is clogged.
This engine has the filter bypass valve built into the block - so oil filters specified for this engine don't have a bypass vavle. Typical older GM design.
Originally Posted by Gokhan
Conversely, if you install an oil filter with a bypass valve, when the oil filter gets clogged, you will have lower oil pressure.
Like I just posted above, that can only happen if the oil pump is in pressure relief. I highly doubt the pump is sitting at 80~90 PSI outlet pressure at idle as controlled by the pump's pressure relief valve - especially with hot 200 deg F oil.
The OP needs to put a mechanical pressure gauge on the engine to verify the function of his dash pressure gauge - just like shown on the service manual page you posted. That's the first thing to verify or people will have all kinds of theories assuming his dash pressure gauge is working correctly and is accurate.
One thing I noticed is that the recommended oil filter for this car doesn't have a bypass valve, which will cause high oil pressure if the oil filter is clogged.
This engine has the filter bypass valve built into the block - so oil filters specified for this engine don't have a bypass vavle. Typical older GM design.
Originally Posted by Gokhan
Conversely, if you install an oil filter with a bypass valve, when the oil filter gets clogged, you will have lower oil pressure.
Like I just posted above, that can only happen if the oil pump is in pressure relief. I highly doubt the pump is sitting at 80~90 PSI outlet pressure at idle as controlled by the pump's pressure relief valve - especially with hot 200 deg F oil.
The OP needs to put a mechanical pressure gauge on the engine to verify the function of his dash pressure gauge - just like shown on the service manual page you posted. That's the first thing to verify or people will have all kinds of theories assuming his dash pressure gauge is working correctly and is accurate.
Originally Posted by ZeeOSix
Originally Posted by Gokhan
One thing I noticed is that the recommended oil filter for this car doesn't have a bypass valve, which will cause high oil pressure if the oil filter is clogged.
This engine has the filter bypass valve built into the block - so oil filters specified for this engine don't have a bypass vavle. Typical older GM design.
Originally Posted by Gokhan
Conversely, if you install an oil filter with a bypass valve, when the oil filter gets clogged, you will have lower oil pressure.
Like I just posted above, that can only happen if the oil pump is in pressure relief. I highly doubt the pump is sitting at 80~90 PSI outlet pressure at idle as controlled by the pump's pressure relief valve - especially with hot 200 deg F oil.
The OP needs to put a mechanical pressure gauge on the engine to verify the function of his dash pressure gauge - just like shown on the service manual page you posted. That's the first thing to verify or people will have all kinds of theories assuming his dash pressure gauge is working correctly and is accurate.
He is experiencing low oil pressure with HTHSV = 3.0 cP (M1 and PP) vs. normal oil pressure with 3.2 cP (Kendall and VAS). He has a high-mileage engine and his bearings are probably worn and they can't maintain oil pressure with a 5W-30 on the thin side. That's why I suggested him to use a Euro 5W-30 with HTHSV > 3.5 cP.
Originally Posted by Gokhan
One thing I noticed is that the recommended oil filter for this car doesn't have a bypass valve, which will cause high oil pressure if the oil filter is clogged.
This engine has the filter bypass valve built into the block - so oil filters specified for this engine don't have a bypass vavle. Typical older GM design.
Originally Posted by Gokhan
Conversely, if you install an oil filter with a bypass valve, when the oil filter gets clogged, you will have lower oil pressure.
Like I just posted above, that can only happen if the oil pump is in pressure relief. I highly doubt the pump is sitting at 80~90 PSI outlet pressure at idle as controlled by the pump's pressure relief valve - especially with hot 200 deg F oil.
The OP needs to put a mechanical pressure gauge on the engine to verify the function of his dash pressure gauge - just like shown on the service manual page you posted. That's the first thing to verify or people will have all kinds of theories assuming his dash pressure gauge is working correctly and is accurate.
He is experiencing low oil pressure with HTHSV = 3.0 cP (M1 and PP) vs. normal oil pressure with 3.2 cP (Kendall and VAS). He has a high-mileage engine and his bearings are probably worn and they can't maintain oil pressure with a 5W-30 on the thin side. That's why I suggested him to use a Euro 5W-30 with HTHSV > 3.5 cP.
Originally Posted by Gokhan
He is experiencing low oil pressure with HTHSV = 3.0 cP (M1 and PP) vs. normal oil pressure with 3.2 cP (Kendall and VAS). He has a high-mileage engine and his bearings are probably worn and they can't maintain oil pressure with a 5W-30 on the thin side. That's why I suggested him to use a Euro 5W-30 with HTHSV > 3.5 cP.
I'd buy that before blaming the oil filter. I'm sure his oil filter isn't 100% clogged and the filter bypass valve malfunctioning at the same time.
M1 full synthetic is HTHS of 3.1 per their latest spec sheet. I can't see a 0.1 or 0.2 difference in HTHS making the oil pressure get cut in half.at idle. Here's some data that shows the oil pressure isn't that sensitive to HTHS ... at least not as sensitive as the OP numbers seem to be. Could be each engine has it's own HTHS vs OP "curve slope", but I just can't see the line slope being as drastic as the numbers the OP has given.
IMO, if Valvoline Advanced give him good OP then just stick with that.
He is experiencing low oil pressure with HTHSV = 3.0 cP (M1 and PP) vs. normal oil pressure with 3.2 cP (Kendall and VAS). He has a high-mileage engine and his bearings are probably worn and they can't maintain oil pressure with a 5W-30 on the thin side. That's why I suggested him to use a Euro 5W-30 with HTHSV > 3.5 cP.
I'd buy that before blaming the oil filter. I'm sure his oil filter isn't 100% clogged and the filter bypass valve malfunctioning at the same time.
M1 full synthetic is HTHS of 3.1 per their latest spec sheet. I can't see a 0.1 or 0.2 difference in HTHS making the oil pressure get cut in half.at idle. Here's some data that shows the oil pressure isn't that sensitive to HTHS ... at least not as sensitive as the OP numbers seem to be. Could be each engine has it's own HTHS vs OP "curve slope", but I just can't see the line slope being as drastic as the numbers the OP has given.
IMO, if Valvoline Advanced give him good OP then just stick with that.
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In my experience with an SBF, going from a 0w-20 to a 0w-40 had less than a 10psi impact on oil pressure hot at idle (not an SBC I know). So I have a hard time with two oils that are maybe .1 off from each other in HTHS and with nary identical KV100's showing that much of a difference.
I have been concerned and curious about this for probably about a couple years now. Thanks for explaining how same viscocity oil can have such variance in pressure. At this point I will stick with the Valvoline and as long as the pressure remains on the higher side between change cycles, as it has with Valvoline, will just "go with the flow". Until there is degradation using the Valvoline, which I have not seen up to now, I will live with it as is.
Thanks to those who read and responded seriously. You have allayed any serious concerns, will switch back to the Valvoline as planned, and prepare to enjoy Easter weekend up on Cape Breton Island. I will also look for a local source for the Kendall Euro.
Thank you
Thanks to those who read and responded seriously. You have allayed any serious concerns, will switch back to the Valvoline as planned, and prepare to enjoy Easter weekend up on Cape Breton Island. I will also look for a local source for the Kendall Euro.
Thank you
I would get a separate, high quality oil pressure gauge for your experiment. As at least one other suggested, you should likely do this test while you are personally changing filter and oil. Do an OCI with Valvoline and a Fram Ultra, and test the oil pressure for 5-6k. Then, drain the Valvoline but do not change the Fram Ultra, and put in the Pennzoil and test for 5-6k. The Fram Ultra will easily be able to deal with that, and eliminate the filter as a source of your measurement concerns. That will tell you right there if it is oil related, or if it was quick-OC filter related.
My apologies if my comment yesterday was abrasive; your initial post on this board with little supporting info makes it easy to discount, as there have been several trolls popping up on the board lately. Welcome to the board, and hopefully you find some answers to your questions.
My apologies if my comment yesterday was abrasive; your initial post on this board with little supporting info makes it easy to discount, as there have been several trolls popping up on the board lately. Welcome to the board, and hopefully you find some answers to your questions.
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