Oil pressure Question

I got a 95 Chevrolet k1500 with new trans. Motor was put in about 7-8 years ago and has miles according to regular driving 140k-160k I’d guess. Stock as far as I know on internals and the rest except the MPFI system.

Cold start (even on a warm day) oil pressure reads 70 psi and will hold there even if I let it warm up for about 5 minutes and drive it will hold there.

And then after it warms up for a while it will hold 40-55 psi at idle and then up to 60-70 psi while driving.

I am on first oil change since I got it still (changed august 20th) and I went with 4qts of Shell Rotella convential 10w30 and 1qt of Lucas oil stabilizer. (Did it mainly for a clean out on first oil change and I am going to send it in for an oil analyze at black stone labs)

Previous owner (a friend of ours) got oil changes every 3,000-5,000 miles and used a 10w30 valvoline.

I daily drive this truck and have been since I got it, I have heard no odd noises at all. I thought I heard a knock on startup some times but I don’t think it could be because it is a lot quieter than a “knock” would be and it’s a hit or miss, sometimes I think I hear it and it ends up going away and other times I don’t.

anyways I’ve read that it’s normal in some places, others not. But really not sure.

Personally I wouldn't worry about it. That does sound a little high for a V8, but my V6 truck will peg the gauge on 80 for a few minutes on a cold start.

My big block has some high indicated oil pressure as well. Readings should be taken somewhat with a grain of salt. I recently added a stock cluster to my Camaro in addition to the pre-existing Autometer gauges. I trust the latter more and they don't read the same as factory.

Aidan Kesler said:

I thought I heard a knock on startup some times but I don’t think it could be because it is a lot quieter than a “knock” would be and it’s a hit or miss, sometimes I think I hear it and it ends up going away and other times I don’t.

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A little piston slap when cold isn't Abby Normal on older small block Chevys (it's almost Halloween, you need to watch Young Frankenstein!). It is abnormal for the later engines like ours with better pistons and metallurgy, but I remember my Suburban being a little noisy on startup in the cold.

The higher pressure on startup is perfectly normal because typically the truck will idle higher at cold temps, so the oil pump will spin faster. Any oil pressure that reads above that red line basically means everything is fine. Oil pumps rarely ever fail because it is a very reliable design and as you can imagine they are very well lubricated. As long as you change the oil regularly no issues should occur there. If you were to see a significant drop all of a sudden it would likely be due to some kind of leak that has cause the oil loop to no longer be airtight. If that happened I would immediately pull over and inspect the vehicle to make sure no damage has happened to the pan or oil cooler lines/filter etc. The other possibility is that the oil pressure sender (located right behind the distributor) has gone bad. This happened to me and the gauge would read very very low (around 20 PSI at idle) and when I hit the gas it would peg over at 80 PSI.

Your oil pressure is exactly what I would expect and hope to see out of it, Mine reads maybe around 65 PSI at operating temp on the road and yours might read a little higher because that oil additive is going to add a significant amount of viscosity to the oil.

As far as the racket goes, as those trucks age and through many heat cycles they can get tiny exhaust leaks in the manifold gaskets that can make all kinds of noises and typically when the metal and gasket heats up and expands often this noise will go away completely. I am battling a pretty severe exhaust leak right now my self and it changes tone after it warms up and you cant hear it at idle anymore.

Erik the Awful said:

A little piston slap when cold isn't Abby Normal on older small block Chevys (it's almost Halloween, you need to watch Young Frankenstein!). It is abnormal for the later engines like ours with better pistons and metallurgy, but I remember my Suburban being a little noisy on startup in the cold.

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My engine has a knock on startup for the first 5-10 minutes it seems and it quiets down a lot when it warms up and its an even knock that's in rhythm with the engine idling not uneven like a regular spun bearing would be. It sounds like it coming from the bottom of the motor, I do have a bad exhaust leak at the header on the right side but I don't think it is that because it doesn't sound like its coming from there. Do knocks start small and quiet and become louder and larger? I am just wondering if my bearings are wearing out or if its just something I shouldn't really worry about.

Also when it's fully warmed up, it's completely gone and not loud but I feel like I can hear some slight rattle/knock in the bottom and I rev it up and it's not loud or louder but when i let go of the pedal it's noticeable if you listen really carefully because it's quiet.

Years ago I had a 70 Buick Skylark with a 350. I got it cheap ($300) because it had a knock and everyone said it was piston slap. Turned out it was the torque converter. So, for another ~$50 I got a good ride. I installed an am/fm/8-track tape player and some 6X9s and went cruisin', LOL

PlayingWithTBI said:

Years ago I had a 70 Buick Skylark with a 350. I got it cheap ($300) because it had a knock and everyone said it was piston slap. Turned out it was the torque converter. So, for another ~$50 I got a good ride. I installed an am/fm/8-track tape player and some 6X9s and went cruisin', LOL

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How could I diagnose what this mysterious hit or miss knock is on startup?

Aidan Kesler said:

How could I diagnose what this mysterious hit or miss knock is on startup?

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Get an automotive stethoscope (maybe use a long screwdriver) and try to find where it's coming from by placing it on the valve covers, side of block, bottom of block/ oil pan, trans bell housing, etc. Hook up a scan tool and see if you're getting any KCs and maybe SA reduction. See when it happens i.e. all the time when cold, when you blip the throttle, accelerate easy/hard, coast, etc. This may point you in the correct direction.

Or, if you're cheap like me, get a long screwdriver. Put the tip where you think the noise is coming from and put your ear against the handle. Be mindful of moving parts when you place the screwdriver and your ear.