ISX Oil in Coolant

[Starlight]

You need to confirm what kind of oil it is. It could be tranny oil. It isnt necessarily engine oil your seeing. Confirm with a sample from the coolant reservoir if your not sure or drain some oil from the tranny. If it is tranny oil then you'll have coolant in the tranny as well as the coolant pressure is higher in the cooler after the engine is shut down but while driving the oil pressure in the cooler will be higher as tranny has a gear pump. Just something to check.