Google says
oil will be 10-20 higher than water:
Typical engine
oil runs around 230°F–260°F (110°C–127°C) in gasoline engines, whereas coolant usually stays around 200°F–220°F.
I can speak from experience that the
oil cooler will reduce oil temp to below water temp... Had I kept the car I would have put in a thermostat to take the oil cooler out of the system. In fact, for street driving just bypass it. Leave the cooler cuz it looks good.