Oil pressure,high then low?Normal?

My first JEEP..............
Hi,I just bought a 2000 Cherokee with 64,000 miles on it 6 cyl.,although the oil looked clean,the previous owner said the jeep had sat for nine months so I did an oil change.I put Quaker State full synthetic 10w-30 in it.
Oil pressure starts out 50 lbs but after a half-hour or so drops down to 25 at an idle.Pops back up to 50 lbs when I drive again(from an idle)

Is that the wrong type of oil to use?
Is that normal?
Is that any indication of the general condition of the engine?

I have used this message board once before and was totally impressed with your helpful knowlage,hope you guys don't mind me tapping your brain again!:dunno:

thats normal. I run around at 40-60 at speed, and down to 25 at idle. normal operating for the 4.0l is between 20-70. pressure release at 75.my 91' is almoast exactly the same as yours and my 96' is very close. The oil thins as it heats, causing what looks like low oil pressure. 20or less bad, 20plus (to 75) good. hope this helps all info is from alldata.com. jim

Yes,Great!
I really like my new(to me)XJ,by the way,what does the XJ actually stand for?
I'm starting to sound like a tourist!
Thanks! Pete(Mike)

XJ stand for Xtreme Jeep, everybody knows that

http://www.naxja.org/forum/showthread.php?t=921398&highlight=quaker+state

not sure about the full syn?

minimum warm idle oil pressure is 14psi, and your well above that. nothing to worry about.
Do some reading about oil filters and oil types. Fram filters don't work well with the inline 6, stick with a quality filter made by wix or similiar. Napa gold is actually made by Wix, and only costs around 10 bucks..Ive noticed less dry starts after extended sitting time(over 10 hours or so), and more consistent oil pressure since swapping from a fram to a Napa Gold (Wix).

Full synthitic is fine in the moter. By my personal opinion I wouldn't use Quaker State (If you decide to use another brand do it at the next oil change). I use Moble One Extended Service 10-30 full Synthetic. I still change it between 3-5k though depending on how many long trips I take.

Oil pressure is as low as 13psi (per the FSM) at a hot idle to 37-75psi over 1600rpm. 75psi is the relief max.

I personally think the XJ oil press. guage is so low quality that it can't be relied upon. As long as you keep your oil level topped off and use good quality oil and filter, I believe you can almost ignore oil pressure. If you are really concerned, I'd install a good quality aftermarket mechanical guage, such as Auto Meter.