At 5k miles I switched over to Amsoil and their high-bypass filter setup in my 04.5. I now have 9k miles and notice when the engine is cold, it runs about 70 psi. After warmup, it runs 55 psi but idle can go as low as 25-30. I was told the spec. is 15 psi at idle. I believe the pressure ran higher with the dino oil from the factory and my father's 01 runs 75 psi after warmup (gauge is pegged at 80 when cold). His has 23k on it. So I am not sure if this is due to the synthetic or not. I thought that diesels are built to tighter tolerances and so would run higher pressure. My Suburban that I traded would run 50 psi. Any comments???

I'm running dino and I get the same warm numbers you do.

I've found that the type and brand of oil filter will make a difference in oil pressure also.

With the same brand of oil and 2 different baldwin B1441 filters, my oil pressure was about 7 psi different between the 2 filters.

Remember that the Dmax oil pump moves a lot of oil, (Higher volume), so you will see more pressure swings than on a stock gasser engine. Also the dampening of the meter movement will affect how the gauge responds.

There are also here that have reported lower idle pressures with snyth over dino, but that data seems to vary from owner to owner.

That seems within reason to me. Mine runs a little closer to 60 psi when cruising at 2100-2500 RPM with synthetic, but your numbers seem fine. I think the '01s run higher pressure, because my dad's '01 does mainly upon startup.

More info please. Amsoil markets 3 different synthetic oils: 15W-40, 5W-30, and straight 30. Which are you running?
BTW, I run the 5W-30 Amsoil and the dual remote bypass filter Amsoil filter set up and my pressures are very much the same as yours. I now have approx. 20K, filter setup and oil in @ 7K, at 16K oil analYsis. Lab said change filters, top off oil and keep on trucking!

More info please. Amsoil markets 3 different synthetic oils: 15W-40, 5W-30, and straight 30. Which are you running?
BTW, I run the 5W-30 Amsoil and the dual remote bypass filter Amsoil filter set up and my pressures are very much the same as yours. I now have approx. 20K, filter setup and oil in @ 7K, at 16K oil analYsis. Lab said change filters, top off oil and keep on trucking!Running the 15W-40, Dirty. Guess it's OK, just seems odd to have a gauge that goes to 120 psi installed and half of it is not used.

IIRC, I have previously read that 01 & 02s had higher oil press than later years, perhaps they still use the same gauge! The oem oil in mine went way up on the gauge also but it was 15W-40.

I've never used the 15W-40 Amsoil, so I can't comment on that.
When I was researching what viscosity to use ( Amsoil was already a foregone conclusion), I called the Amsoil tech dept., reasoning that since they sold both, their advice should be unbiased.
The tech rep stated that given my stated use (lots of cold start up, short trip, around town with occassional towing of 7K# TT), he said 5W-30 would give better start up lubrication and the hot film strength of Amsoil 5W-30 exceeds any 15W-40 dino oil sold. He further stated that if I encountered increased oil consumption or too low hot idle oil press., it would indicate changing to 15W-40.
Since I have only added 1 qt. in all those miles and oil press is above min. at hot idle, I'm happy.:ro)