06 Silverado low oil pressure question

[hlb14]

Over the past 3 days I've noticed that during cold startup my oil pressure is lower than normal. At startup it will fluctuate between 10 and 20 but after everything is at normal temperature it will rest at 35 at idle and reach 45 to 50 during accel. The motor sounds normal, no ticking or knocking. Truck has 158k, during the last oil change I had the tech add Lucas engine oil stabilizer. I've done lots of reading about sudden loss of oil pressure pointing to the sending unit. Has the oil additive made the oil so thick that it doesn't get a good reading til the oil is warm?

[nightrunner]

I'm assuming this is a 1500 and not a 2500/3500 with the 8.1l 496 big block. Or a v6. If it is a small block v8 it should have more pressure than that, but that's with 10w30 oil no additives. Is your oil level good?

Most likely the sending unit. Has the gauge cluster ever been replaced? There was a recall on the servo motors in them to cause some of the gauges to not read correctly.

[hlb14]

1500 5.3L, not the original owner so not sure about the cluster Edited January 10, 2015 by hlb14

[nightrunner]

When everything is right that engine will pull 70-75psi at WOT high rpm (4,000+ rpm) and oil up to temperature. Either it's an oil issue ( which I would put 10w30 or 5w30 in next change), pump (unlikely but possible) sending unit (possible) or gauge cluster ( most likely IMO). It should have higher pressure though when the oil is cold and the pressure drop some when it warms up to operating temperature and the oil thins out.

[Dustbuster]

It's possible I just went through the same thing.. Usually if the sending unit goes out it pegs the gauge to 80. Additives will also loosen up gunk in the engine which in turn clog the screen on the oil pump intake. I just got almost 380 k miles out of my 5.3. The oil pressure would be ok when cold and would drop to almost zero if u didn't keep the RPMs up. After it warned up. Once it was running it would idle at 25 and sit at 45 on the highway.
I flushed the engine out, changed oil twice and the pressure still wouldn't come up.. Not wanting to be stuck in the middle of no where w a blown engine, I Ended up swapping the engine out. Life is good. I have a guy in Robertson co that swaps Chevy engines out in a day or so. If u want his number pm me. Edited January 10, 2015 by Dustbuster

[swim615]

In my opinion the lucas most likely made your oil thicker (higher viscosity) and with the cold which also make the oil thicker is making it have lower pressure until the engine and oil warms up. Most likely if the stepper motor in the instrument panel were going out it would (sometimes) not reset all the way to the zeroed position and would work its way higher and higher . (Every time it goes up it thinks that is the 0 and restarts from there until it tacks out the gauge) Sometime acting normal and others not but very noticeable none the less.

[peejman]

What weight of oil is in it? Is it garaged or outside?

[raildog]

Pick up manual pressure gauge and a pice of hose with male 1/8 pipe thread and a copler to connect gauge to hose remove oil pressure sending unit and hook up hose gauge setup run engine see what you come up with that will tell you if it is the engine or something electrical

[hlb14]

What weight of oil is in it? Is it garaged or outside?

5\30

Going to try and get the oil changed tomorrow as well as check the pressure manually. Hopefully that will get all of the Lucas out. Fingers crossed