First off a little history. I have an '06 F250 CC SRW 4X4. I bought it new in October of '05. I always do the oil changes and fuel filter changes myself at intervals a little sooner than called for in the manual. The truck has never been in the shop for repairs. After reading all of the horror stories about clogged oil coolers and ruptured EGR coolers I was getting a little worried about my truck. I still, after 75000 miles, have the ford gold coolant in the truck and decided to just do a coolant service and keep the gold stuff in there. I installed a coolant filter after the coolant service and went out and picked up a Scanguage II. I hooked it up last night and drove the truck to work this morning. On the way home, the outside temps were about 90 degrees. My drive home is 20 miles and I was doing about 70 mph. I was pleasantly surprised to see my deltas stayed at 5 to 7 degrees. With the ECT at 188 and the EOT at 193 most of the way.
So, am I lucky or just a typical 6.0 owner? I had to post a good story about a 6.0. I'm tired of all of the 6.0 bashing.
I too lucked out and bought a truck that was maintained very well by the dealer. The 1st owner had a 100,000 mile service plan where everything was done by the dealer. The next 50,000 miles are unaccounted for, but in the 20,000 miles I've owned it, it's been strong. I am just having to deal with the frame components showing wear at 168,000 miles. I think a lot of attention was paid to the motor, but regular maintainence on the frame-end was neglected. I'm talking brakes, suspension, steering, etc... That's what I'm working on now, getting all of those issues replaced.
I'll admit, I was a little worried because I did my first coolant service at 75k but when I saw that delta I was pretty relieved. I also just ordered some REV-X so I guess I'll see if all of the hype about the stuff is true.
Rev-X is great stuff! My rig springs to life instantly, everyday, since I put Rev-X in it!
It sounds to me like your thermostat is getting weak, 188 degrees cruising at 90 degree heat is a little cool. Should be 190-193, proper temps promote good combustion, keep an eye on it.
Really...? 2 degrees...? That is no cause for concern at all.