Temps after driving on the highway for 30 minutes.
ECT 180
EOT 205

Is that normal?? I just checked and I'm pretty low on coolant (inch below the tick mark) and this week I'm going to get the coolant flushed and replaced. I don't think I have a coolant leak because I haven't flushed my coolant in..forever. But are those temps because of lower coolant or an oil cooler problem?

 

You have 2 issues. ECT should be 190+ and your EOT should be less than 15° higher than ECT.

The low ECT is a sign of needing a new thermostat.
The high EOT is most likely due to a clogged oil cooler,

 

Moneypit is right on the money... I agree 100%

 

I concur, however, I would first change the t-stat and see what that does for the temp. spreads. If not within the 15 degree max. it's time for an oil cooler also. If an oil cooler is called for I would then do a chemical flush first and then change the oil cooler.

 

A revision to the coolant level puts it at. 3/8 inch below add mark when cold. There is a TSB and a sticker available at the dealer parts counter. I believe the new degas bottles have been revised so if it's been changed (on your truck) it could be marked correctly. If it's an '05 you may want to do some other stuff while you're in there. Chances are temps have been high for a while an the EGR cooler (if it has one) would be cooked too. Up graded aftermarket EGR coolers are available that are much stronger than the original, or even a delete may be a good option depending on EPA testing in your area. STC fitting is a 60 something dollar part that can strand you and it's easy to change with the intake off. Some would also mention standpipes and dummy plugs. That's a good preventative measure but they are under the valve covers and could be done later without too much fuss. the turbo oil feed and return lines have been updated (you'll have those in your hand doing the oil cooler). And almost forgot the fuel pressure spring update. It will raise your fuel pressure a bit and possibly improve running and reduce injector failures.

I completely agree with 69cj and the rest of the guys on your current temp situation.