I've got the kind that screw in from the side.
Ground side, the threads of the screw look nice and clean/shiny.
Hot side they're dull, red/brownish in the grooves.
Couple times I've had starting problems that were cured by wiggling and/or tightening the hot side.
Seems like the screw is ripe for cleaning but I can't think of what to do for the female side except put some kind of electro-conductive goop on the male side threads.
Is there a stock solution for this?
Or is there even a problem?