The 6.0L Power Stroke delta-T test is the single most useful check on the engine - it tells you the health of the oil cooler (the root of many 6.0L failures) without pulling anything apart.
Why the oil cooler matters
The 6.0L oil cooler plugs over time, raising oil temperature and starving the EGR cooler, which then overheats and cracks. Catching a restricted oil cooler early prevents that chain.
How to run the delta-T test
With a scan tool, compare engine oil temperature (EOT) to engine coolant temperature (ECT) at operating temperature under load. A healthy engine holds the two within about 15 degrees. If EOT runs more than roughly 15-20 degrees above ECT, the oil cooler is restricted.
What to do with the result
A large gap means it is time to replace the oil cooler - and, because you are in there, the EGR cooler too - with a proper coolant flush. A small gap means the oil cooler is still flowing well.
Frequently asked questions
What is a good delta-T on a 6.0L?
Roughly 15 degrees or less between oil and coolant temperature at operating temp. More than ~15-20 degrees indicates a restricted oil cooler.
Can I test the oil cooler without tearing it down?
Yes - that is the point of the delta-T test. It reads the restriction from temperature data.
Run the delta-T test before chasing 6.0L overheating or EGR trouble - it points straight at the oil cooler.
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