2004 6.0 diesel ave 17mpg in town

The leak is on the right side of the motor, at the rear and on the lower side of the valve cover. It's not the valve cover but a small electrical connection below the valve cover. What is that, glow plug, injector, or something else?
Other than the very small leak it is an awesome truck. It pulls very well.

 

This problem is quite common. It's the glow plug harness. Mine was leaking and they replaced the entire harness,,,,no more leak.

 

Thanks for the reply

Joe