2000 silverado low oil pressure

[Stevotlmn]

Recently purchased a used 2000 silverado, 167000 miles. Day after buying oil pressure drops and light comes on at idle, increase rpm's pressure goes up to appx 25 to 30, Talked to previous owner and was informed he was using 20/50 weight oil anything lower the light would come on. I replaced oil with 10/30 and a bottle of lucas and pressure went up and stayed good for the next 2500 miles then the pressure started coming down again at idle. Replaced the sending unit, didn't fix it. Checked pressure on the top with a separate gauge, pressure was around 9 or 10 I think at idle. Some say excessive wear which would make sense when I increase the oil to 20/50 and pressure goes up but now after the most recent oil change when I used 20/50 the pressure at 2000rpms is only around 20 and it is turning the light on at idle. The other weird thing is that when I shut the truck off all needles on the dash go to zero, but the oil pressure gauge stays where it is or goes all the way to the right, but never to zero. I have looked at a lot of online forums and seen this issue a lot but no concrete solution, some say oil pump, but then say it was replaced and didn't fix the problem. Any suggestions will be greatly appreciated. Thanks!!

[8.1HD/ALLISON]

Sounds like it could be oil pump. Could also be engine wear. Won't know till you try a pump, or tear down and measure clearances. Its not the cluster if the manual guage says the same as the dash.

[Stevotlmn]

Can the oil pump be replaced from below? Again, I'm hearing different stories on how to replace. One told me I had to lift the engine out "some" to remove. Also, after last oil change, noticed some metal shavings on the tip of oil plug. From the oil pump maybe?? Or something else?

[Carder09]

Sounds like you might have a dash cluster issue. I think there was a recall on some of the gmt-800's, probably best to get it rebuilt or replaced.

[jaredlucky16]

Junkyard engine