Your oil isn't fully warmed up. It can take a long time to get oil temps to match coolant temps. The coolant temp seems a little low too. I would be more concerned about your thermostat opening too soon.
Thats what I figured too, and I replaced the t-stat yesterday with a 192* one. How long would the truck need to be driven in order for the oil to warm up? Farthest I have driven is about one hour on the highway since I have owned it.
There is quick ways to warm them up, a winterfront will help. If you want to warm it up for testing or some other reason you can run it down the road in 3rd gear, that will put the rpms right about 3000. But for the time being I wouldn't worry about it. This just means that your oil cooler is doing an excellent job of cooling your oil.