I would use silicon grease as an alternative to vaseline, the sort that is sold for potable plumbing.

Wouldn't silicon reduce conductivity?

My understanding is that these connectors have high contact pressure, and the wiping action as it makes will move the silicon out of the way.  Petroleum jelly is also an insulator (and flammable).

Ok, that makes sense.  We've used Dielectric silicon grease before but reluctant to smear the contacts with it. Maybe we should be a bit more brave. 

I see no reason why silicone grease would repel water any better than Vaseline or bog-standard grease. Whichever sort you use, the contact between the prongs and sockets will wipe it away. What you need is a good dollop of the stuff which prevents the water from getting near in the first place.

I see no reason why silicone grease would repel water any better than Vaseline or bog-standard grease. Whichever sort you use, the contact between the prongs and sockets will wipe it away. What you need is a good dollop of the stuff which prevents the water from getting near in the first place.

Tbf, I still use either vasoline or grease and it hasnt been a problem to date.