Well, darned, I put over 150,000 miles on my truck and trailer when I was hauling cars and another 30,000 all those years racing, I never put a drop of grease on the ball. Same ball (I'm a cheap bum) and the trailer coupler was the same one as well. I did have to change the coupler one time after I let someone borrow my trailer and he bent the tongue and coupler. Didn't notice any wear on the coupler, and the chrome was still good on the ball. It was probably the quality of the chrome on the ball that "saved" me.

I just hate to think of all those "unsafe" miles I logged on my truck and trailer without greasing the ball.
However, given the current quality of available parts around these days, I would probably grease the ball if I was going to do much towing now. Gene