Just finished reinstalling a remanufactured 5.7 hemi with OEM oil cooler. At idle, my coolant temps are normal (180-200) but my oil temps slowly creep up, all the way past 270 Fahrenheit according to the digital dash display. Not driving, just idling in the garage/driveway.

The cooling fans are kicking on as expected. There is sufficient, fresh coolant of the correct type. I believe the thermostat is working properly too since my coolant temp is reading normal. I don't think it is an oil temperature sensor issue, because I can feel my valve covers and pan getting way hotter than what is normal from the hot oil itself.

Worth noting that I have stainless long tube headers installed that are not coated/shielded in any way. Would the ambient heat from the headers be enough to cook my oil like this? Again, my coolant temps are normal at 190-200 degrees.