no

no if its a warm climate your going to want to use 50w90 works better

what would a hot climate be...arizona???mexico??? would recommend 10/40 with an additive..

actually it is okay to run 10-30 motor oil because if i am not mistaken Jeep recommends either 5-30 or 10-30....I can't remember which one of those two they do but the only difference between those is the viscosity at cold temperatures...the though they only have recomendations for up to temperatures of 115 degress Farenhiet...and most important thing to know...don't mix different brands of oil together and try not to mix different weights of oil though mixing weights of oil is not too harmful at all becasue i use mixed oil weights in my vehicle...

If west coast use as 10w-30 if you are shooting for FE, else a 10w-40 was originally spec'ed for the 4.0

50w90 is like gear oil or rear diff fluid, dont use that, too thick.
5 or 10 w 30 should be fine, I would recommend a thicker wieght oil for higher milage engines. You could also use 15w 40 too...but I wouldnt use anything thicker than that.