What oil for 97 jeep 4.0 ?

[Huie83]

Thanks MNgopher,

Right now running 10w-40, pressure sits @ 30-40 psi warm idle, 45 psi at speed and about 50-60 psi until warmed up.


Is higher oil pressure bad? I think max on these engines is 72 psi, right?

 

[TapSnaporNap]

FWIW on an old thread, these motors ALL develop a bit of a lifter tick. And I am convinced it's because 99.9% of the people that drive them don't know about the Flat Tappet Camm/ZDDP scenario. I changed out my noisy cam and lifters, that were visibly worn and it's as quiet as a mouse now. I'm using some Quaker State 10w30 synthetic "4x4" oil that I got on sale with the Comp Cams ZDDP additive and it's as quiet as a mouse. I put a high lift cam (and springs)in it so it probably does have a bit more spring pressure.

 

[jorton]

Awesome first post. I read the whole story and I don't even own a jeep!

Anyways, I hope Jeep folks can get extra protection simply by switching to 10w-40.