My 90 5.0 has 40 psi first start up cold as it gets warmer it's steadily drops. Driving it's like 5-7 psi is this normal? Thank in advance

 

When my 302 did that all the mechanics I talked to said it was probably caused by worn out main bearings.

 

+1 to this. Cam bearings can do it too. Toss in some Lucas at the oil change and just keep driving.
This stuff :
Lucas Oil 10001-1 - Lucas Heavy Duty Oil Stabilizer - Overview - SummitRacing.com

 

ten four, thanks for the replys. i was just curious cuase iv heard some say its not good then iv heard some say its fine just keep the oil in the good zone and drive it.

 

If your using 5w30 time to step it up also. I had a GMC 350 that had a bearing knock as well as what your saying and I drove it for another 50K miles before we traded it. When I say knock im not talking a faint one. Full bore someone is at the door and wants in ... You could hear it over the exhaust 30 feet away. At idle when warm the Pressure would serge 1-5 PSI with the knock. Could not kill the bugger and tried hard.

My 351 now has it hot at idle w/5w30. Knock and pressure drop.... I can just barely hear this knock but its there with the gauge fluctuation, if you listen for it. 15W40 full to the brim it does not knock or drop pressure. 10W30 with the lucas its fine also. 10w30 alone will do it hot.

Next oil change try the lucas with your normal oil. Add the full bottle it will most likely stop doing it. The bottle is more then a quart. So note it when filling. She still has a long life left, no fears ...

 

yeah my ol trucks only got 123k on it for being 21 years old i say not bad. im actually debating changing the oil today. so ill step up in oil weight and go from there. thanks for the info ill keep the lucas in mind if this oil change doesnt effect any thing.

 

I have this same problem, except my oil pressure gauge never goes up...NEVER...I thought maybe it was just the gauge that needs to be replaced. because I noticed my engine temp barely gets past cold as well. so I figured maybe there was just something wrong with the gauge. Any ideas?

 

I dont know what year the change is but that factory gauge reads mid normal at 5PSI and its on or off. At some point in the years here it was a real gauge and moved with pressure changes. It does sound like you have a cluster issue if it also reads cold and its not. Put a real oil gauge in that puppy and you will always know your good or you need to shut it down. same with the temp gauge.. I would not bother fixing the factory one unless you are selling it.