Oil Psi When Running And Idleing?????

Can Anyone Tell Me Whats The Psi When The Truck Is Running And What It Should Be When Idleing???..my Truck Starts Off At 42psi When Started And Then Drops To 20psi When Idling After Its Been Driven For A Little While Til The Engine Warms Up But Recently Its Dropped To Aarond 18at Idle.....i Must First Say It Is Only 10 Degrees Will The Temperture Affect The Psi After Running Or Can I Be Looking At A New Oil Pump????? Thanks For The Help .....happy Holidays....

Mine is at 40psi-idle and 60-70psi-running. I have a 2000 2wd 1500

What year make and model is your vehicle?

i have a 1995 silverado 4x4 ...i spoke to my mechanic and he threw in a 10w-40 after he changed my intake manifold gasket....does this seem right to anyone ????I dont want to second guess him but i dont want to screw up my motor or have a big expense later on ....if i need a new oil pump let me know please..and if you think hes ripping me off let me know cause i dont want to trust him and spend alot of cash if hes jerking me around and waiting for it to go so he has the business of replacing it and charging me big money????im sure u all know were im coming from just wish i had the know how id do it myself....thanks guys

Not sure what prompted him to change your IM gasket but heavier oil is a hail mary fix for low oil pressure. Mechanics typically do it on high mileage engines that are worn and showing low pressures, it's not a bad way to fix it but it's not an actual fix either because all it does is mask the problem whether the problem be a worn oil pump or engine.

As far as your pressures I'm not sure what the specs call for but I wouldn't be too worried about the 18 psi at idle with a cold engine in cold weather. If the 10w40 helped your pressures quite a bit then you may need an engine overhaul or oil pump.

10 PSI for every 1000 RPM's is plenty enough oil pressure starting at 15 PSI being the lowest

I have a 92 K1500 (same engine as yours, 5.7L TBI), and these trucks don't run as high of oil pressure as the newer trucks (99-up).

Once my truck comes up to temp., it idles (in gear) at about 15-20 psi, and runs on 35-40 psi. As long as the pressure jumps (literally) back to 30-40 psi as soon as you touch the gas (and I mean just barely touch it too, not rev it hard) then you're fine.

However, if it takes it a while to build the pressure, then you need bearings, or really, just an overhaul.

Edit: Aslo, even if you do have a problem, it more then likely wouldn't be the oil pump, it would be the bearings. However, if you did get an overhaul, its a given to change the pump (and the pistons, and the rings, and all of the bearings).