scatgo

Should I go synthetic? Or stick with standard type oil. My oil pressure will drop to 10 at idle so i am thinking synthetic might make that worse.

JPXJMOAB

I run synthetic blend every other oil change, helps keep things a little cleaner and smoother... However it will find every leak your engine has.

mschi772

You should fix that oil pressure situation asap. Specs say that the 4.0 should never drop lower than 13 psi when warm and should be 37-75 psi at/above 1600 RPM.

Conventional vs synthetic? It doesn't matter, and many "synthetic" oils aren't even as synthetic as people think they are anyway. It's been covered soooo many times, and there are even websites devoted entirely to motor oil, so I'm not about to get into all of it again.

Bottom line: after tons of research and experience, my top recommendations are, in no particular order...

Shell Rotella T6 5w40 (Group III)
Pennzoil 5w30 or 10w30 (conventional)
Castrol Edge 0w30 (Group IV)

cruiser54

What brand oil filter is on the Jeep?

rgr4475

That was my question too.

OP, tons and tons of people run synthetic without problems. You may have another underlying issue.

cruiser54

Like a cheapie oil filter. seen it before. Or, a bad oil sender.

watertrucker

I replaced the oil pressure sending on my `96 XJ last week for a similar issue. Pressure wouldn`t go above 25 psi. New sender: 45 psi going down the road, 40 psi. at idle. 167k on HO 4.0

djb383

Any time there is a question about oil pressure, the absolute 1st thing that should be done is to test/verify oil pressure with a known accurate mechanical oil pressure test gauge. How does the test gauge compare to the dash gauge.

Once u know for sure what your oil pressure range is, at both idle and off idle and it's with-in factory specs according to the test gauge, then one can safely play around with various oil filters and oil viscosity.

Remember, pressure does not equal lubrication....flow equals lubrication.

http://www.supramania.com/aehaas/

rgr4475

Yes. It happened to me personally when I first bought the jeep. Put a cheap oil filter on it (Yes you know the brand but god forbid we upset people and tell the truth) and it was killing my oil pressure. Switched to a quality filter and everything has been right as rain since.