In this video I fix a sticking accelerator linkage on my W108. When I took it apart it was apparent that someone had used grease on the linkage. When that dries out, it gets hard and stops the linkage from working properly.
According to the old Mercedes-Benz service manuals the bushings should be oiled with oil from an oil can after every engine wash. So I took everything apart, cleaned it with brake cleaner and oiled with with a machine oil that I have.