I purchased a heavy duty swaybar for my Volvo and it came with a thick green sticky lube that the instructions said to use on the bushings (the bushings were polyethylene).
I can't remember exactly what the lube was called but it was for use on ships and saltwater resistant.

As for the MBZ, mine makes a little groan sometimes and I plan to lube the bushings next time I have the belly pan off. To properly lube them, you need to remove the bushings and coat the entire contact surface.