Oil on main wiring harness near battery

I know this has been discussed somewhere else that a lot of members find the connectors around the battery box get a oily covering and that it is probably the grease used to waterproof the connector. Well I just done a battery change and yes the connectors are coated in oil which is definitely engine oil because it smells like oil. The only place it could be coming from is that the oil must leak from the gear position indicator and travels along the outer sleeve of the wiring harness and out onto the connectors.
Any thoughts

or an oil change done by a stealer, its messy if you dont use al-foil

I'd love to know where it comes from. Mine are always coated in oil, I can clean them but a few months later they are coated again. She never drips any oil on the deck though, so where ever it comes from it's the slowest of weeps.