In my previous comments, I pointed out that the hitch is the best path you have to ground the wiring. I DID NOT say that you should rely on that for ground. You can use the inadequate little white wire if you want. It's not a good ground. You can use a jumper cable if you want. It's not a good ground unless you grind off the paint
and rust from both contact points, and assuming it doesn't fall
off on a bumpy road. You can try all sorts of things, and you should have as good a wired ground as you can achieve. However, you still can't get past the fact that the hitch is the best, most reliable source of ground available to you. Don't rely on it as your primary ground, but also don't use things that interfere with it. Axle
grease is one. Bad idea. A good ground is your friend.
Reese (and others) make hitch lubricant for this purpose. To quote from the Reese product pages (for Reese Hitch Lubricant and Reese On The Ball Lubricant), "Just a few drops of this extreme pressure lubricant on your hitch ball will eliminate dangerous friction – without interrupting electrical
Don't assume that just because some other things are slimy that they work as well for the purpose. And, if you have a properly adjusted coupler in good condition, and a properly mounted hitch ball of reasonable quality, and are towing within the weight
capacities for both, you should never see spalling, galling or loosening balls, whether you lubricate or not.
(Qualification here -- this applies to the weight
of trailers most of us are towing. If you are towing in the heavier classes, you certainly could see galling. The need to lube goes up with weight
, as the friction goes up under the same conditions.)
To sum up, I am not saying I am against lubricating. There is no denying that lowering friction is a good thing. I choose not to do it, because I am not experiencing wear on my towing components. However, you may choose to lube it for yourself. Great -- just clean and relube it before each trip (to clean up road grit), and use a product that is designed for the purpose.