2006 PSD CC 4wd, 134k.
Generally my truck runs cool if anything. Mid 60's low 70's temp in my area. Usually my ECT is 186-188 or so with EOT in the 196-200. When it does get hotter say ECT 196 or so the ECT will never be more than 7-10 degrees higher.
Yesterday driving home from work, 62 degrees. Just cruising the ECT is 198-204 and EOT 212-218. At one point it did go a a delta of 15 degrees very briefly.
It was almost as though the truck was not shifting into overdrive. I noticed the boost gauge was higher than normal even though my foot wasn't in it at all. In fact I backed down to like 60mph and watched my Scan Gauge closely. I pretty much babied it home.
I'm aware of the EGR/ Oil cooler issues, but I've been watching the ECT/EOT closely and have never seen a delta that would cause concern.
Could it be something else? There were no codes thrown.
Where should I start?