UK Nissan Repair Questions? Ask a Mechanic Online.
Hello, I hope you are well.
You are correct, usually this is the oil cooler.
The pressurised oil finds its way into the coolant, via the heat exchanger assembly section.
Other causes have been known to be cylinder head gasket or cracking, but not often.
I would initially, yes.
If this is all the information you need, please rate the answer ;)