[Jeeper6]

...sounds familiar...here is my story...I am in my 2nd WK2 diesel as my previous one met with a sad ending...that was a 2014 build.
But, that engine would run really good coolant temps and oil temps...when not towing oil temp would sit anywhere between 85c and 95c depending on terrain....coolant was always around mid 80's as well.
Towing the "magic" temps for that engine was oil at 104c, coolant at 94c, never varied much beyond that, maybe a degree or 2 higher on grades.
This was after an oil cooler failure where oil filled the cooling system and had to be flushed a few times with replaced oil cooler.

Anyway, after the demise of that poor thing I secured another WK2 diesel but a 2015 model but pretty much identical with a few extras.

When I drove that one the temps seemed ok, higher than the previous engine but didn't concern me too much. It did not have a tow bar when I bought it, which was why I bought it, so on went the towbar to drag the van.

First trip away towing my caravan I was horrified when the coolant temp sat in high 90's on the flat roads with oil temp pushing 110c most of the time.
On a reasonably long grade heading into Biloela the oil temp hit 128c with coolant at 115c...not pushing at all so backed off some more dropping a gear.

Anyway...chasing the temp issue, I fitted new radiator cap...made no difference. Had the radiator flushed and new coolant...no discernible difference.
What I did note was the cooling fan wasn't coming on when it should...but it was coming on flat out screaming when ever the DPF was doing a burn.

I decided to try replacing the thermostat with a brand new Mopar $400.00 special, hoping that might fix it...it didn't...it actually made is worse...temps went higher.

There was a recall carried out onmy Jeep among others to reprogram the TCM...which yes, I think it had to do with the vehicle throwing itself in to Park if you opened a door, it was the S49 recall I think, the offshoot of that was a glitch in some Jeeps that affected the cooling fan where it would go ballistic when doing a DPF burn but was not coming on to cool the engine when it was supposed to.

I spoke to the local Jeep Dealer service manager, he was an OK guy, had dealt with him before...and he also drives a WK2 and tows a camper.

I took the Jeep in, they reprogrammed the fan operation so it came on when it was supposed to. It was much better after that but still not ideal temps.

I decided to pull the thermostat out of my old WK2, and put it in my current WK2. Before putting it in I had 3 thermostats on the bench so I hot water tested them. They all read 98c on them as the opening temp.
The one out of the old Jeep would start opening around 80c, both the others were at least 95c before letting water in.
After putting the old thermostat in I now have the temps I was chasing...towing 104c oil, 94c coolant, not towing oil will be as low 80c along with coolant...but it took a good radiator flush, new radiator cap, the Jeep Dealer recall correction, and replacing the thermostat to fix the problem.

(On a side note, I know of 2 high profile Jeep CRD owners that had experienced oil temp as high as 135c when towing up long grades...way too high for me to be comfortable.)