Some have had good luck with a washcloth, warm water, mild soap and elbow grease to clean the MB-Tex periodically. I've had good experiences with Mr. Clean Magic Eraser pads myself. They really get the grime off of the seats and panels, in addition, they can easily remove accumulated brake dust on rims.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.