Failure mode - Ford 6.0L Power Stroke

Engine oil cooler clogging / failure

Reliability tier: verified - verify before ordering, see /disclosure/

Symptoms

engine oil temperature (EOT) runs well hotter than engine coolant temperature (ECT) under load
repeated EGR cooler failures
coolant in the oil or oil in the coolant (internal cooler leak)
overheating during towing or grades
reduced heater output

Root cause

The engine oil cooler sits in the valley and coolant flows through it before reaching the EGR cooler. Its coolant passages are narrow and clog with the silicate sludge / casting debris described in fm-6-0-coolant-system-neglect. A restricted oil cooler both overheats the oil and starves the EGR cooler, which is why the EGR cooler keeps failing until the oil cooler is addressed.

Diagnosis

with a scan tool, compare EOT and ECT at steady highway load: a delta above roughly 15 F indicates restriction (SME to confirm exact threshold)
check for oil/coolant cross-contamination
inspect coolant for the sludge that causes it

Fixes

replace the oil cooler; thoroughly flush the cooling system at the same time ()

oil-cooler (part category - specific model not chosen)
oil-cooler-gasket-kit (part category - specific model not chosen)

install coolant filtration to prevent recurrence ()

coolant-filter-kit (part category - specific model not chosen)

for high-power or heavy-tow builds, an external / relocated oil cooler kit ()

external-oil-cooler-kit (part category - specific model not chosen)

Prevalence

near-universal