All I know is if Whelen or FedSig has a p/n for a can of rotator lubricant, I want it for bragging rights!
Far as what to use, I've gone through a buncha stuff. White Lithium is what I spec for a lot of car stuff. I use straight lithium on my rifles. But, I've used graphite in the past, seems to work.
Problem is temperature swings. Either piss hot from being in the sun to start with, or chilled due to driving in rain / sleet or overnight. Then hot when those 55 watters fire up.