Just another view from outside the box
Just purchased a 06 Amarillo. Traded up (or down, how ever you want to look at it) from my 97 F250. I did a lot of research and bought it any way. It has 104000 miles on it and I'm in the process of doing the coolant flush.
Anyway, being and X Deere mechanic, I was just thinking ...... the oil in the engine runs hotter than the coolant. So, could it be possiable that the gelling effect of the (unserviced) antifreeze in the cooler occurs from the (Cooking if you will) extreme differance of the coolant VS oil temp. And over time clogs the cooler, advancing from where the oil is the hottest entering the cooler to the discharge side. Ie;resulting in the mystical 100,000 mile window of cooler problems.