Just returned from my first long trip with Scangauge on the truck. I watched it regularly, had mostly 8-10 degree differences. High temp was 224F climbing out of a steep canyon, 10 degree difference at that point.

I did have at least 2 times when I saw a 17 degree difference, once 20 degrees, all 3 for just a moment.

Is the 15 degree delta a hard and fast rule?

 

15* is max straight and level. Hill climbing and towing are not included.
8* is excellent. What are your temp deltas after coldsoak?

 

The 15* is where Ford says the oil cooler should be changed but, the measurement is supposed to be taken under specific conditions. Just because you see a 20* or even higher delta doesn't mean there is somthing wrong with your truck.
Here's the meat and taters from the TSB (thanks Blade!):
Oil cooler test


5. Road Test For Restricted Oil Cooler – Setup and Observations:
a. Install integrated diagnostic system (IDS) select engine coolant
temperature (ECT) and engine oil temperature (EOT) PID’s on IDS
Datalogger
b. Carefully drive the vehicle at wide open throttle (WOT) / high load to
achieve maximum boost.
NOTE
FOR ACCURATE TEST RESULTS, ECT TEMPERATURE MUST BE GREATER
THAN 190° F (88 °C) WHEN MEASURING THE ECT AND EOT MAXIMUM
TEMPERATURE DIFFERENTIAL
NOTE
PERFORMING THIS TEST STEP OUT OF SEQUENCE CAN RESULT IN
INACCRUATE TEST RESULTS. THIS CAN BE CAUSED BY A LEAKING EGR
COOLER ALLOWING (HOT) COMBUSTION GASES TO ENTER THE ENGINE
COOLANT AND ARTIFICALLY RAISING THE ECT READINGS.
c. Observe ECT and EOT PID’s on IDS Datalogger. EOT maximum
temperature differential might occur at throttle tip-out.
(1) If EOT is within 15° F (8.4° C) degrees of the ect, go to Step 7.
(2) If EOT exceeds ECT by 15° F (8.4° C) or more at any time
during the test, go to Step 6
Step 6
is to replace the oil cooler

Step 7
is to test head gaskets.

Without any additional TSB’s specifically for clogging oil coolers, the above statement
has been adopted by the community as the benchmark to determine a clogged or clogging
oil cooler. For the lack of a more in depth test process we will assume that a delta of less
than 15° Fahrenheit your oil cooler is operating within specifications. If it is above 15°
Fahrenheit oil cooler maintenance is required, which may include replacement of the oil
cooler.

 

I wonder if Ford has changed the thermostat set point. I changed mine out last year after failing to operate above 185-186F during the delta test and the new thermostat seems to operate at the same range. With mild ambient temperatures, unloaded, level ground, 60mpg it averages about 186F. Perhaps it's just my system but everything is stock.

 

Phantom, I will check the cold soak temps in the morning. Where are you in Arizona?

Rusty, thanks for that info. I will work on that tomorrow, have to get on the freeway anyway.

 

I ran 50 degree spread for a year, but I have no egr cooler to blow out. My spread now is 6-8.

 

No should be 190* thermo open temp

some put in thermo that open at a little hotter cant remember the temp though diesel needs the heat for combustion thus better MPG

Your 186* could be the Gauge or even the temp sensor off alittle

your close at 186* you might even be at 190* and dont know it cuz the gauge or sensor reporting wrong

 

There are quite a few of us running consistently at 186 in the cooler weather, so far I haven't found the reason. Using ScanGauge for my temp readings. Haven't tried replacing the sensor yet. Supposedly I have the latest flash that's supposed to set a CEL on a spread of 15, no CEL yet but I've seen over 15 frequently on the SG.

If you happen to figure it out please enlighten us! I'm on a new tstat too.

 

It would be great if it were falsely reading 4* lower . That would bring my deltas down to 5-6* (providing the EOT was accurate)

 

Once again, deltas are only accurate after a 15 to 20 mile highway cruise, all components heat saturated and readings taken on level ground. My deltas are consistant empty or towing as long as those ctiteria are met. No wot, hills or cresting. Just good flat, level highway.

 

Dan, IMHO i feel it is important to establish a baseline delta, as indicated above, and see if it is climbing. If it is getting into the lower teens, I feel a good long highway flush may help if performed early enough. Some have had luck in lowering their deltas. I lowered mine a little even with a 30 degree spread. Yur delta doesn't seem bad, but make sure you check like 69cj et al said. Here's a thread for the flush.


VC-9 Before and after; Worth the money - Ford Truck Enthusiasts Forums

 

Cold soak EOT is 93.5, ECT is 92.

My new thermostat was also at 186 in cooler weather, now it is consistently higher with hotter ambient temps.

I did some test runs in cooler weather a few months ago but never got up to a decent ect. It should be in the 90s here today and will run into town on the freeway and see what I have.

Glad this is clarified, seeing a few 17-20 deltas kind of concerned me.

 

Did my run on the freeway after a good 20 minute warmup, ran mostly 10-12 degree difference, 212/200 at the highest temps, level terrain, 90F temp, 70 mph for about 5 miles. Delta was 6-8 when I left the freeway and drove through town to my destination, things cooled down to a norm of about 198/192 or 190.

 

Don't think I'd be too concerned. Just watch deltas and ignore anything not after full heat saturation and on completely level terrain.

 

Thanks for the reply, yep, I think I will consider this a baseline reading and just watch it for any changes in the wrong direction.