As You Can See Both Are Installed In Water Flange...So They Both Are Water Temp Sensors
One (Big One) Is For ECU Engine Coolant Temp Sensor..... The Small (Single Wire ) One Is For Your Meter (Cluster/Gauge) Sender
The Oil Is Not Leaking Out From Them But From Any Seal From Top.....!!
Technically And Practically...They Can't Leak Oil Because They Are Water Temp Sensors ..Can Leak Water Not OIL ...