I thought my oil pressure was normal..however i've been told it looks low from my gauge...its typically below the half way mark and it will increase at higher rpms..is this normal?

 

Sadly yes, try changing out the sending unit, its pretty easy and straight forward, if it still reads low try a mec. gauge, if its still low, you can try cleaning the oil out, sea foam, about 200-300 miles then change the oil again, if that doesnt help, might be looking at a few other issues.

Oil Pump
Cam Bearings
Crank Bearings

what i listed before are the cheaper fixes

 

What are some symptoms of this...as in what will it cause the jeep to do? Cause it runs strong...starts kinda rough but thinking that's from a plug issue...

 

I have about 40lbs at start up...And then as she reaches operating temp, it will drop to 20 while im at the stop light idling.. and it will travel back up to 40-45lbs. Are you having readings like this??

 

1. Age
2. Previous user (services)
3. Mileage and over all use style (driving habits)
4. Service error (damaged the sending unit)

Could be any number of things, a bad part, the person who owned it before you didn't keep up on the services, or did it half *****, or just drove it like it was stolen.
As for the bearings that could be a little more serious. But again goes back to services. I would say while your at it, check your transmission fluid and your differentials as well.

 

Oil pressure spec for the 4.0 is as follows:

*Not less than 13 psi at hot idle
*Between 37-75 psi over 1600 rpms

If you are in this bracket, you are okay. If you're not, best to verify it with a mechanical oil pressure gauge. They can be rented from many of the big box parts stores.

 

Yes the are readings im having

 

Then you're good to go.