I think there was a post about this a while ago, the author said it worked for him but cant remember what the experts said about it. I think that most of the noise on the 7750 rotor is when is spins in the non winding direction (very freely) and the grease may deaden the sound and slow the spin in that direction but may also:-
a, More force may be required to wind the watch by the rotor as the automotive grease would provide more resistance than the thin watch making oils that are used.
b, May pollute other areas of the works that do not need the grease.
c, i have heard that gen swiss, chiss or swinese 7750s also have loud rotors any way.
I hope this helps, have a good search and see if you can find the original thread.