No oil pressure on start up.

[Blk00ss]

I would almost guarantee its the oil pickup tube O ring. This is an issue on every single 5.3 and 4.8 GM made. Its an easy fix (4 wheel drive is more difficult) once you get the pan off. Just remove 3 bolts that hole pickup tube, replace O ring (be sure to oil it) and reinstall. Just had to do this a month or so ago on ours (171K). Started noticing oil pressure when cold would sit around 20psi. Odd seeing how its entire life it idled at 40psi. Dropped pan, replaced O ring, replaced pan gasket. Now she idles at 40psi and runs just under 60psi while driving. It also helps lifter tick if you've noticed any. Replacing that O ring just helps oild the engine better

 

[dnt1010]

From what I understand GM sent out a bulletin to change the Oil Pickup Oring as a maintenance item at 150k increments. I need to do mine but it looks like a good bit of work. I might get a couple of estimates from my local garage today to see if I want to do it myself or have it done. I know full well if I do not take care of this soon I will lose the engine due to poor lubrication at startup.

 

[robgreg75]

From what I understand GM sent out a bulletin to change the Oil Pickup Oring as a maintenance item at 150k increments. I need to do mine but it looks like a good bit of work. I might get a couple of estimates from my local garage today to see if I want to do it myself or have it done. I know full well if I do not take care of this soon I will lose the engine due to poor lubrication at startup.

what years did that effect?

My 2010 5.3L always had lower pressure than my 2001 5.3L. it is at 269K miles now and it has about 25-26psi at 500 rpm idle when I put in new 5-40 oil, at 1200 cruising it is at about 35psi. It goes up over 40 if above 2000 rpm. But like I said this one has always been lower. My 2021 with 22k miles gets down to almost 20 psi at idle but goes up to around 60psi above idle.

 

[Meccanoble]

what years did that effect?

My 2010 5.3L always had lower pressure than my 2001 5.3L. it is at 269K miles now and it has about 25-26psi at 500 rpm idle when I put in new 5-40 oil, at 1200 cruising it is at about 35psi. It goes up over 40 if above 2000 rpm. But like I said this one has always been lower. My 2021 with 22k miles gets down to almost 20 psi at idle but goes up to around 60psi above idle.

I thought these engines took 5w-30 ??

 

[iamdub]

My 2021 with 22k miles gets down to almost 20 psi at idle but goes up to around 60psi above idle.

It's normal. Your '21 has a variable displacement oil pump to reduce pumping loads when the pressure's not needed.

 

[robgreg75]

I thought these engines took 5w-30 ??

Yes that is recommended but with 269K miles I now use a little thicker oil, I started around 200K using the thicker.

Plus this is Texas and it is hot most of the time. Some people will argue about what thickness to use, I use 15w-50 in one of my cars. If you look at the actual curves of temperature vs viscosity being in a hot climate vs a cold one it you can see that even the thicker oils are usually easier to pump at startup in a hot climate than the thinner oils in a cold climate.

 

[iamdub]

Yes that is recommended but with 269K miles I now use a little thicker oil, I started around 200K using the thicker.

Plus this is Texas and it is hot most of the time. Some people will argue about what thickness to use, I use 15w-50 in one of my cars. If you look at the actual curves of temperature vs viscosity being in a hot climate vs a cold one it you can see that even the thicker oils are usually easier to pump at startup in a hot climate than the thinner oils in a cold climate.

They also factor in power used from pumping the oil when determining an oil weight to spec for an engine. Heavier oil increases fuel consumption, although it's nothing the end user will never notice. But, it's still a loss in efficiency (MPG) so they spec the lighter oil. IMO, the lighter oil brings with it a sacrifice in engine longevity and it's all just more factors they're trying to balance when specifying an oil. I'd rather take the .0003% (arbitrary number) loss in fuel economy and have better protection for my engine.

10W-40 full synthetic Diesel oil FTW.

 

[donjetman]

I'm in TX and I switched from 5W30 to 0W20 at my last oil change, (174k miles). I always do used oil analysis (UOA) so we'll see in 6 mths to a yr how my L92 6.2L likes it or not. Over at BITOG forum a smart fella did a thread about viscosity. Thinner oil, especially until the engine oil reaches full operating temperature (200*f), flows more volume thru the passages etc, which can be a good thing? We'll see?

 

[iamdub]

I'm in TX and I switched from 5W30 to 0W20 at my last oil change, (174k miles). I always do used oil analysis (UOA) so we'll see in 6 mths to a yr how my L92 6.2L likes it or not. Over at BITOG forum a smart fella did a thread about viscosity. Thinner oil, especially until the engine oil reaches full operating temperature (200*f), flows more volume thru the passages etc, which can be a good thing? We'll see?

We have variable displacement oil pumps, now we need variable minimum viscosity oil.

I feel that the increased bearing clearances of my well-used 5.3 coupled with my ported high-volume pump allows plenty of volume for the heavier oil I run. I'm no scientist, but I believe that if the oil were more water-like, such as 0W-20, it would require more volume and the resulting pressure to achieve the same shear strength. Sure, the 0W-20 at XX psi might be plenty sufficient while not presenting any undue drag and my choice is overkill. But, I run my stuff hard and if the oil can protect in the horrid environment of a Diesel engine for hundreds of thousands of miles, then it's plenty robust for me.

If I'm wrong, well, as I've said before, this 5.3 owes me nothing. But my UOAs say all is well... So far.

@donjetman, have you noticed any change in your MPG since the lighter oil?

 

[donjetman]

ops