From the manual covers export KJ CRD's
From what I can see if you are in Australia and you are running high temps you might consider 10-40, probably synthetic is best and low ash if you can find it coz thats good for particulate filters and catatalytics but most importantly check the rating of the oil in your owners manual, note weight was not specified in mine, i referred to the owners manual for the oil specification then selected the weight of oil to match the temperatures i operate in from the Jeep service manual. I think typically in the US, because of EPA, they use thinner oils than are possible. often in the 5w30 range. The manual for export versions definitely said 10-40 as an oil weight, its tucked away a few more paragraphs down in the manual beyond the intial blurb about this.
From my experience the engine is quieter and smoother with 15-40, though Id prefer 10-40 in winter, and as I have heard of a couple of engines losing conrod bearings and generally falling apart and being replaced using 0-40 (low viscosity oils) etc I know where my preferences lie at the moment. If you change your oils at proper times with filters turbo lubrication probably wont become an issue.
Currently I am using Diesel magnatec 15-40 and touch wood (picture me with my hands on my head) seems fine. Remember though that if you do not operate with a good EGR or modified egr you are dumping a tremendous amount of soot into your engine, someone thought it would be better in your engine than on the road or in the atmosphere or something.
ITs worth noting I am in Perth and operate here, to the eas and all points north so that gives you some idea of the operating temperatures im working with. Generally no ice or snow, mostly warm to HOT.
Just my 2 cents worth