In article ,
DJM wrote:
Try xyol (xylene) the paint thinner. I was told by a Xerox repairman they
used it on copier rollers when they got hard.

I have used it and works for me.

Yep.

TEAC used to sell a rubber rejuvenator for cassette decks that was
essentially xylene. A suitable substitute can be bought in the US as a
paint/gunk remover called "goof off" in the yellow metal can.