These MB bars are very unusual in the way they slide through the bushings, instead of the traditional 'bolt type' endlink setup. This design sets the bushings up for a short lifespan, but at least they are cheap and easy to replace. Seems like greasable polyurethane bushings would be ideal here.

Had the same situation on my 124.

Very rough surface on bar and lots of wear on the rubber.
Figured the new bushings would not last long like that.

Cleaned the bar up as best as I could with emery cloth, and applied a silicone grease, which is compatible with the rubber.
Recently examined, and found bushings are still in good shape after 15k.

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1986 300E 5-Speed 240k mi.