I am working on a mack truck GU series with a MP8 engine, the driver is complaining that the engine oil temperature is hitting the red on the guage, especially when loaded.
I found two inactive codes that indded indicated that the engine oil temperature was high.
The amazing thing is that is coolant temperature is normal although the oil temp is running hot.
The driver mentioned to me that if he turn on the cab AC the temperature stays normal.

Any ideas what is wrong here guys

Thanks