GM LS engine oil pressure again

This was discussed a few weeks ago. Less
than normal oil pressure on a 5.3 with
afm. I had the same issue with my 2008
5.3 when I bought it 4 or 5 years back.
Issue was the delco filter on it.
Pressure was real low. 7 or so at idle
and 17ish at highway speeds. After
changing to a different filter it's been more
like 20/40 for the last 35k miles.

So, a few weeks back I bought a 2010 2500
with the 6.0. 230k on it. Oil pressure
just seemed weird. Around 17 at idle, but
only 22 to 25 on the highway. Just didn't seem quite right. So
after seeing the post a couple weeks back
I stopped at NAPA and picked up the long
27045 oil filt sprint6 reccomended. I
just swapped filter. Previous owner said
he had a synthetic oil change and it still
had 1500 miles left on the sticker and 60%
on the dash.

Oil pressure immediately jumped to 30 to
35 idle and 45ish on highway. I'm a lot
happier with those numbers. This just
really kind of blows my mind though. Do
these filters cause such a restriction
that the pressure relief on the pump is
just dumping oil? I've seen it twice now,
so I know it happens. Just wondering the
why behind it all. I've seen this discussed on other forums, but never an explanation as to why.

The offending filter on the 6.0. I
haven't cut it open to look yet. I did
the delco on my other truck, but didn't
really see anything that stood out to me.

It would be a good question for Sam's Garage, out of Atlanta Ga.On Saturday morning,you can hear on the net, he streams it,Starts at 8:00-10:00, There are two guys there, both first name of Sam, It's a car problem talk show ! I get it thru Yankton S.Dakota, radio, 570 AM .

On the 5.3 AFM engine, the oil pressure is double regulated. You have the regulator on the pump that regulates the pressure to the bearings, then there is a second regulator that controls the pressure to the AFM system. The AFM system is only designed to operate at a max of 60ish psi. The AFM manifold is where the oil pressure sensor is. The AFM oil pressure is what is actually being displayed on the dash, not main line oil pressure. A late 6.0 may have the second regulator in the pan, haven't had one off so I don't know. Somehow, a filter restriction limits oil to the second regulator, dropping the AFM pressure. Even GM does not know why. There is a GM bulletin stating the filter issue, but does not explain why it happens, and says they won't be pulling filter stock. What ever it is is trickling down to the aftermarket, Delco filters started with this problem 10 years ago, but now I have taken off Purolator, Fram, and now I see Mighty added to my list.

The only other thing I have seen on an LS cause low pressure is spun cam bearings. Does not happen often, but have seen it a couple times. Those have low pressure all the time, though.

I wouldn't be calling a dime store filter an AC DELCO.

I had 2 different trucks do this. The first was a 2008 5.3 that had an AC DELCO filter on it. The second is the 2010 6.0 that I pulled this Mighty filter off of.