BatsTDK
Full Access Member
What oil weight were you running before?
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You have no problems. That oil pressure is fine. When you say, "almost" 5 pounds lower, do you mean at 4 or 3 or 2 or.....?
What brand and model oil filter did they put on it?
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patateB-5
Member
5w30 Mobile 1
BatsTDK
Full Access Member
Are you sure they put in what you asked for? Mine idles at about 38psi and around 45-50 when I hit the gas. Yours doesn’t seem too far off. Filter maybe?
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patateB-5
Member
To be more accurte, Idles at about 35-38. Giving it the gas barely gets to 40. Which makes me hopefully think it's a weak sending unit. I'll switch the sending unit and if I don't see an improvement, I'll dump the oil and go to Rotella like I had wanted before......
IF the reading is correct, you have no problems.
SnowDrifter
Full Access Member
35 at idle is perfectly dandy
It's my opinion that >30 hot idle is just dandy on these vehicles. 25 is where I start looking for issues. Even though lower is technically 'in-spec,' it will anecdotally cause problems.
m1 5w30 is on the 'thinner' side, having a viscosity of 10.37cSt as per blackstone labs. Note that the range for XXw30 when hot is 9.3-12.5. So, a 5psi difference between oils in that acceptable range isn't out of the ordinary.
It's also normal for oil to have a 'bell curve' of viscosity when in an engine. When new, lighter / more voltatile components will flash off over a couple hundred miles, making it slightly thicker. Then as it's used, the oil will shear down and become thinner again. It's a little difficult to pick up on the analog gauge, but if you have a digital readout, you can watch it happen in real-time. It's weird.
Fun fact: the difference in viscosity between cold and hot is the viscosity index. It's an inverse relationship - so the lower the ΔV between cold and hot, the higher the VI. This trend continues as the oil heats above 100c, there high VI oils won't thin down as much as a low VI oil. This can show up where oils commonly referred to as 'too thin', like a 0w30, will have a higher viscosity and keep oil pressure up better under high temperatures than a 'texas thick' oil like a 10w30, because of the difference in viscosity index. 0wXX oils were avoided for a long time because they had a tendancy to shear down and get thin with use - they weren't as stable. But advancements in synthetic modifiers have made this largely a problem in the past. 'Tis why I run a 0w40 in mine year-round. It actually flows better at 0c than say... M1 5w30. The crossover point for this 6c / 43f.
It's my opinion that >30 hot idle is just dandy on these vehicles. 25 is where I start looking for issues. Even though lower is technically 'in-spec,' it will anecdotally cause problems.
m1 5w30 is on the 'thinner' side, having a viscosity of 10.37cSt as per blackstone labs. Note that the range for XXw30 when hot is 9.3-12.5. So, a 5psi difference between oils in that acceptable range isn't out of the ordinary.
It's also normal for oil to have a 'bell curve' of viscosity when in an engine. When new, lighter / more voltatile components will flash off over a couple hundred miles, making it slightly thicker. Then as it's used, the oil will shear down and become thinner again. It's a little difficult to pick up on the analog gauge, but if you have a digital readout, you can watch it happen in real-time. It's weird.
Fun fact: the difference in viscosity between cold and hot is the viscosity index. It's an inverse relationship - so the lower the ΔV between cold and hot, the higher the VI. This trend continues as the oil heats above 100c, there high VI oils won't thin down as much as a low VI oil. This can show up where oils commonly referred to as 'too thin', like a 0w30, will have a higher viscosity and keep oil pressure up better under high temperatures than a 'texas thick' oil like a 10w30, because of the difference in viscosity index. 0wXX oils were avoided for a long time because they had a tendancy to shear down and get thin with use - they weren't as stable. But advancements in synthetic modifiers have made this largely a problem in the past. 'Tis why I run a 0w40 in mine year-round. It actually flows better at 0c than say... M1 5w30. The crossover point for this 6c / 43f.
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patateB-5
Member
Thanks you
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patateB-5
Member
Thank You for the info..
bayareadude84
Full Access Member
His is a 2006 and it DOES NOT require Dexos !! Dexos is for 2011 and newer GM Vehicles
I was taught this at GM service dept I worked at few years ago and this story in cars.com backs it up
bayareadude84
Full Access Member
Yes it's one of the most TOP RATED filters out there !! I run the XG3675 on my 01 burb with 2-3 4000K OCI's on it. I would NEVER run ANY filter pass 10K miles !! IMO a $10 filter is not worth passing "trash" into your $$$ engine !!
bayareadude84
Full Access Member
To be more accurte, Idles at about 35-38. Giving it the gas barely gets to 40. Which makes me hopefully think it's a weak sending unit. I'll switch the sending unit and if I don't see an improvement, I'll dump the oil and go to Rotella like I had wanted before......
If you havent done your oil pick up tube seal Fel-pro # 72401 I HIGHLY recommend it !! Cost under $3 right now on Amazon and you have to drop oil pan and pickup tube to replace it. But better do it now then when it fails and take out your oil pump !!
My 2001 with 200K mile was HARD like a rock and broke into pieces when my mechanic replaced it a few months ago when I first bought it and was doing all PM's on it !! YIKES I dodged a bullet on that one !!
VERY common issue with these vehicle !!
Dave
pa31p
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This is one of those threads that will give gravitational pull to just about any forum.
oil when it’s on sale and do it yourself you can do a full synthetic change for about $40 including the filter on your truck. buy something that meets spec.
just about any synthetic of the correct weight for your car will do.
These cars are pretty forgiving to the oil as there’s no turbocharger in it.
You can spend a lifetime reading opinions about what oil is good or bad but hard to go wrong if you stick with the correct weight.
oil when it’s on sale and do it yourself you can do a full synthetic change for about $40 including the filter on your truck. buy something that meets spec.
just about any synthetic of the correct weight for your car will do.
These cars are pretty forgiving to the oil as there’s no turbocharger in it.
You can spend a lifetime reading opinions about what oil is good or bad but hard to go wrong if you stick with the correct weight.
bayareadude84
Full Access Member
Welllllllllllllll I tested now discontinued Rotella Gas/truck fully syn (I had 200 qts of the stuff from clearance sales) on my crown vic police interceptor and my 01 burb and I never in my life heard so much engine clatter after 1000 miles or so !! So I quickly flushed out changed that crap oil on both cars. Now the crown vic is running M1 and Suburban running Castrol GTX magnatec and NO MORE clatter and both have super smooth startup !! There's a guy on youtube who is a Ford MASTER tech and he had same horrible results with Rotella in his grand marquis
MassHoe04
Full Access Member
I usually run whatever is recommended in the manual by the manufacturer, unless there is some specific reason to do otherwise.
So for as long as my 04 valves and lifters are happy, I'll keep using 5W30 synthetic (Pennzoil, M1, Castrol... whatever is on sale).
If the engine is good on that, I'll stick with it.
In my 05 Jeep, I ran conventional oils. I was changing every 3k miles on that.
While I had intentions of doing every 3k on the Tahoe, I have been going longer. So I'll stick with synthetics on that.
So for as long as my 04 valves and lifters are happy, I'll keep using 5W30 synthetic (Pennzoil, M1, Castrol... whatever is on sale).
If the engine is good on that, I'll stick with it.
In my 05 Jeep, I ran conventional oils. I was changing every 3k miles on that.
While I had intentions of doing every 3k on the Tahoe, I have been going longer. So I'll stick with synthetics on that.
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patateB-5
Member
Happy Holidays everyone........ 
