2008 6.0 Vortec, low oil pressure?

Messages
28
I know that this subject has been beaten to death over the internet, but still leaves me confused with no definitive answers. Only things that I know for sure, are the factory minimum specs, and the old rule of thumb 10psi per 1000rpm.
Since I have a great trust for the knowledge that the folks on BITOG have, here goes.



So my truck is a 2008 Chevy Suburban 6.0 with 90k on the clock. I'm running Mobil1 ESP 5w-30 and a WIX XP oil filter, been there for 4000 miles. Oil pressure sensor changed same time with the oil.

Cold start, oil pressure is 40psi. 1500rpm on highway, starts slowly dropping when the engine warms. It will stay in 25-30psi @ 1500rpm after 20 miles when the engine is properly hot. Idle psi when fully warm is 20psi or a hair over. Needs ~2500rpm to get near 40psi hot.
Everything works and sounds perfect.

Some say it's fine, some say it's half what it's supposed to be. I am aware of the common problem with the oil pickup tube o ring, but I've understood that the symptoms go the other way round (low psi cold, normal hot).

What do you guys think? What kind of oil pressure are you having on those engines (2007-2014)?
 
I have the exact same engine in a 2008 3/4 to Suburban. It is closing in on 210,000 miles. In warm weather the oil gage takes 3 seconds to reach 40 psi. At highway speeds it is at 40 psi. At idle, it is about 35 psi. That is the “ normal” for mine. It used to stay at 40 psi all the time. I ran Synthetic 5w30 for 12 years. Using. 5w40 oil makes very little difference, maybe two psi at idle higher. Almost no difference at highway speed. Recall there is a spring in the oil pump that regulates the pressure.

Some have said to add two quarts of oil and park downhill to submerge the O ring in oil to check it. A person could do this just prior to a oil change.

Some have said to change the screen below the oil pressure sensor. If you haven’t done that year, maybe consider it. Also you need to get a definitive oil pressure with mechanical gage. I believe Jeggs or Summit sells a screw-on boss to screw on in place of an oil filter and is threaded for a mechanical gage.

If you have four wheel drive, it is a pain to drop the pan to get at the O ring. If not, it’s not that bad. With only 90,000 miles I would invest the money to drop the pan. That engine has a long life ahead of it. :)
 
Messages
55
Location
Indiana
Pressure is low for the engine 35-40 psi at hot idle is the norm. I would investigate. Be sure to check with manual gauge as the cluster gauge can lie.
 
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21
I ran 0w40 on my LS1 a long time ago. It brought the pressure up a bit, but not much. I never worried about it because it was a great engine.
 
Messages
716
Location
MN
I've found that GM oil pressure gauges are far from accurate, I've always gone by the fact that it's showing oil pressure, pressure goes up with the RPM's and I can't hear the lifters ticking at idle. Had plenty of them live a full long life without any unusual issues.

My current 6.0 had 40psi at idle hot or cold since day 1 and it's never shown more than 50psi at any RPM, previous one would read 25psi hot idle and climb to 50psi, had one truck where the needle lived between 20-30psi regardless of temp or rpm. Didn't matter what oil I used and the engine never complained, sold it at 240,000mi running great.
 

0burb8

Thread starter
Messages
28
Good info, I thought about switching to 5w-40, but if the increase is barely noticeable maybe not worth it.

I'm propably going to have my buddy change the o ring, maybe would be a wise thing to replace the oil pump at the same time, since you are dropping the pan and going through the trouble? Oil pump relief valve stuck also seems to be a common cause. Is there a fix for it or just throw in a new oil pump?
But before anything else I have to make sure with a mechanical gauge.

Snagglefoot-no oil pressure sensor screen on 6.0 engines.

I would maybe let it be like that, but because it has low miles and I plan to keep it several years I'm going to fix the problem. I think that it would maybe run perfect as is for years, but it would bother me all the time seeing the low oil pressure. So for the peace of mind too.
 
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6,581
Location
In the Garage...
You changed the sensor at the same time as the oil? What brand sensor? I wouldn't even mess with it. Even though my 2017 is different it has a variable displacement oil pump it will sit between 25-30 PSI at hot idle. In my LS1 I have seen a 15 psi difference between a GM sensor and an aftermarket one. I would not worry unless you were seeing under 20 on that engine.
 

0burb8

Thread starter
Messages
28
You changed the sensor at the same time as the oil? What brand sensor? I wouldn't even mess with it. Even though my 2017 is different it has a variable displacement oil pump it will sit between 25-30 PSI at hot idle. In my LS1 I have seen a 15 psi difference between a GM sensor and an aftermarket one. I would not worry unless you were seeing under 20 on that engine.
I actually had another problem previously, couple times when I started the engine, I would get no oil pressure until I gave the engine a little rpm. Somehow I thought that oil pressure sensor caused it, turned out to be a bad oil filter after all. I replaced it with a Dorman sensor, I can't tell if the old one was original but I still have it.

Btw, I remember reading somewhere that back in the day somebody was concerned about these same type oil pressure readings, he took a brand new Express Van for a test drive to see what the oil pressure was, it was at the same range.
 
Messages
6,581
Location
In the Garage...
I actually had another problem previously, couple times when I started the engine, I would get no oil pressure until I gave the engine a little rpm. Somehow I thought that oil pressure sensor caused it, turned out to be a bad oil filter after all. I replaced it with a Dorman sensor, I can't tell if the old one was original but I still have it.

Btw, I remember reading somewhere that back in the day somebody was concerned about these same type oil pressure readings, he took a brand new Express Van for a test drive to see what the oil pressure was, it was at the same range.
Yeah when I did the LS6 intake in the WS6 I broke the sending unit and put an aftermarket sensor in. It read low. I went and got a GM one, read what I was used to.
 
Messages
7,846
Location
Hudson, NH
My 6.0 lq9 is always 35 at idle, 45 on the highway using 5w30 syn. I'm in several 6.0 groups and the oil pump is just as likely to be the problem as the o'ring in the 6.0. The oring is more of a problem in the 5.3. So if it were me I would replace the oil pump with a melling high flow along with the o'ring.
 
Messages
5,443
Location
Suburban Washington DC
Good info, I thought about switching to 5w-40, but if the increase is barely noticeable maybe not worth it.

I'm propably going to have my buddy change the o ring, maybe would be a wise thing to replace the oil pump at the same time, since you are dropping the pan and going through the trouble?

Oil pump is built into the front cover. Go to 10W40, it added a good 5 psi to these readings on a 200,000 mile truck.





Will probably try 5W50 the next oil change.
 
Messages
5,238
Location
Fort Worth, Texas
You changed the sensor at the same time as the oil? What brand sensor? I wouldn't even mess with it. Even though my 2017 is different it has a variable displacement oil pump it will sit between 25-30 PSI at hot idle. In my LS1 I have seen a 15 psi difference between a GM sensor and an aftermarket one. I would not worry unless you were seeing under 20 on that engine.

Mike, Your L96 still uses the fixed displacement gerotor oil pump.....The Gen V DI engines are using the variable displacement vane oil pumps.
 
Messages
5,238
Location
Fort Worth, Texas
My 6.0 lq9 is always 35 at idle, 45 on the highway using 5w30 syn. I'm in several 6.0 groups and the oil pump is just as likely to be the problem as the o'ring in the 6.0. The oring is more of a problem in the 5.3. So if it were me I would replace the oil pump with a melling high flow along with the o'ring.

Just as common on the 6.0L engines, Lot more 5.3L engines made & that might make it seem like they're more prone to it.
 
Messages
5,238
Location
Fort Worth, Texas
Overfill the crankcase with @ 3 quarts of oil, Jack up the rear of the truck high as possible, Start engine & allow it to reach normal operating temperature.

*If low oil pressure is still present.....It is NOT the Pick Up Tube O-ring.

I don't trust Dorman at all, It may be wise to put the OE sensor back in as they only have 2 modes of failure.....Leaking & Internally shorted (Signal to 5vdc reference).

*I've seen the AFM block-off O-rings cause low hot oil pressure, These are part of the Valley Cover & not sold separately.
*Pressure Regulator Valve stuck (Cracked open). Part of the Oil Pump.
*Worn Cam Bearings, Especially on VVT engines with their gigantic Cam Gear/Phaser.
 
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572
My 200k 4.8 has 32-34 hot idle, 40 cold. 47-50 cruising with m1 0w40. It was as low as 28-30 with 5w30 just before the last oil change. I tried the jacking up the rear and overfilling it. It maybe added 1-2psi but not 100% sure. This is just with the stock oil pressure sender and torque pro displaying it. The truck has 8700 hours so it could just be a bit of overall wear. I believe it used to always be over 40 when I drove this truck years past.
 

0burb8

Thread starter
Messages
28
Thank you guys. First I'm going to put back that OE-I think-sensor, then hook it up to a mechanical oil pressure gauge. Then the oil overfill trick.
If these fail to show anything conclusive, maybe it's time for oil pump replacement?
In my mind should not be possible that the cam bearings are worn out at that mileage.
It has that VVT and no AFM, though.

I can't remember the hours on my engine, but remember calculating it vs the mileage and was OK, no tons of idling.
I can report the hours when I get to the truck.
 

0burb8

Thread starter
Messages
28
Thank you guys. First I'm going to put back that OE-I think-sensor, then hook it up to a mechanical oil pressure gauge. Then the oil overfill trick.
If these fail to show anything conclusive, maybe it's time for oil pump replacement?
In my mind should not be possible that the cam bearings are worn out at that mileage.
It has that VVT and no AFM, though.

I can't remember the hours on my engine, but remember calculating it vs the mileage and was OK, no tons of idling.
I can report the hours when I get to the truck.
2803 is the hour reading.
 

0burb8

Thread starter
Messages
28
I spend a lot of time reading at a Yukon/Tahoe/Escalade forum. Your engine is fine. That's normal healthy oil pressure. You have nothing to worry about.
I have a 6.2 L92 in our 07 Yukon Denali with the same oil pressure readings as yours.
This is what my gut tells me too.

I've spent a lot of time also reading different Chevy, LS etc. forums and yes, the opinions and oil pressures that folks have seem to vary a lot. And that leaves me with that uncertain feeling.

I also learned, that engines without the AFM, do not need or have to operate on the same pressure that the AFM engines. AFM needs higher oil pressure.

Then there's the VVT, which my engine has. Too much pressure, or volume, will harm the VVT functioning and that's why those engines need the certain pressure range to operate properly. Completely different oil pump for VVT compared to AFM.

Still I would like to see more opinions, I'm really debating with myself about to pull the trigger on a new oil pump.
 
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