Been taking a few trips empty lately so I've got mine...

I ignore the Differential until ECT is stable at or above 190.4 and EOT gets at least 5 deg above. I've had some miles to "play" with this now and running 65 on flat-ish freeway I'm 6.5 to 7.5 degrees higher EOT to ECT. Ambient temps in 80s... Oh and I've checked 48 hour cold soak and w/i 1 degree of each other (although it is oil that is higher, so maybe I can subtract 1 degree?! ).

Oil cooler was done about 5K ago (old one was likely fine, I was doing the "old" test and thinking it was marginal). VC-9 flush prior to new cooler and Final Charge CAT EC-1 coolant and distilled H2O after. Factory original Thermostat. Installed XDP Bypass Coolant Filter after as well...

I actually was dissapointed -- I kept reading of these guys with 2-4 degree spreads. Oh well, that's what mine does....

 

Keep in mind lol I live in western Nc ,,, so flat isn't exactly flat

 

No load, city, idle, etc, 0-4 degree delta ranging from 196-204

65mph pulling tandem enclosed trailer, 4-8 degree delta from 198-208

New OEM oil cooler and bulletproof diesel egr cooler in January 2016. Stock T-stat, factory ford gold coolant.

 

Since replacing thermostat with a Mishimoto 200° it's been consistently 7-8* at 65MPH. Just came back from upstate NY a few weeks ago... (about 400 miles). Stayed at 204 and 211 all day! Going up I was towing a 30' RV, consistently, 210 and 217* on the flats. The oil cooler was replaced about 7-8 years ago (warranty). Also had studs put in at that time. I change the coolant every 20,000 now and do have a coolant filter.

 

Bought my 06 with 93k miles. Stock oil/egr cooler. Been running 8* diffs ever since. Sometimes as low as 6 and some as high as 10. Mostly 8. I'm at 144k now. I did switch to ELC and add a coolant filter. But that's it. 192 ECT/200 EOT on average.

 

Mishimoto 200 degree stat, IPR external oil cooler, 200-202 ECT, 209-212 EOT. When pulling camper I get 1 15-17 spread. I have been worried that my spread was too great but it sounds like I am right in line with mot people.

 

I had my oil cooler replaced and a BP EGR cooler installed in early April. All fluids changed. After new piston (see "Broke Down in Boise") repair and both head gaskets done with studs a week later, all fluids were replaced again. My EOT and ECT temps are now never more than 7 degrees apart, even climbing 8500 ft Galena Summit (Idaho) at 40 mph with a 3500 lb slide-in camper. Most unloaded temps are within 1.5 degrees of each other. This is probably the best they will ever be, but it will be interesting to track the wear on this motor for the next 150K.

I am going the 5W-40 and Archoil 9100 route this next oil change so will be following the effects after that as well.

 

< 20k miles on radiator and < 5k on oil cooler. Running a coolant filter. My coolant system is clean enough to drink from.

4 to 5 delta at 60 mph.

 

I just got my oil changed on Saturday and literally when that was done I began seeing 10-13 degree deltas on the highway.... and as soon as i get off id see 7-10. Happened quite suddenly. If I stay off highway and stick to around town im like 2-5 degrees when i get up to temp. Im hoping and praying my oil cooler isnt clogging again. Relatively fresh coolant and its ELC. No coolant filter though. When last cooler was replaced idk if restore+ was done.

 

What oil and filter are you running?

 

Delta will change with engine load, weight or speed. It's more pronounced as more of the oil cooler is compromised, a proportional change.

 

 

 

Here is a great article on heat transfer of various new and used oils.

The heat capacity AND the thermal conductivities do change as an oil ages. To a degree, they tend to improve as the oil ages (related largely to dispersed soot content as I understand it). While a 15W40 MIGHT have different characteristics than a 5W40, it will almost certainly depend on the oil formulation BEYOND just the viscosity difference. Anyway, as an oil changes, the oil viscosities tend to decrease (until they begin to sludge up). If oil gets too thick, then the pumping rates will drop and this affect will affect the heat transfer rates. I doubt that this happens within the normal range of oil change intervals!

All that said, these difference are probably ONLY in the 5-10% range. Different oils with the same viscosity can vary with regard to their thermal characteristics.

http://www.oetg.at/fileadmin/Dokumen...9-LOCKWOOD.pdf

 

Are ALL of your observations done AFTER you have FULLY gotten the engine up to operating temperature? The temperature differential data is of little use to us until the oil exceeds the coolant temp and then stabilizes.

I agree with Jack - the change in maximum temperature differential will change some with engine load .... this change will definitely increase depending on the degree of oil cooler fouling (and depending on ANYTHING restricting coolant flow through the oil cooler).

My differentials do not change a whole lot as I go from 65 mph to full WOT throttle. I feel like I have a very clean system. I have not evaluated the effect of heavy towing on the temperature differential in my truck. Having too much fun w/ the SRL + tune.