See also:

Tips for driving with DISTRONIC PLUS
Important safety notes The following contains descriptions of certain road and traffic conditions in which you must be particularly attentive. In such situations, brake if necessary. DISTRONIC ...

Mercedes-Benz M-Class Owners Manual
...

Cleaning the exhaust tail pipes
Impurities combined with the effects of road grit and corrosive environmental factors may cause flash rust to form on the surface. You can restore the original shine of the exhaust tail pipe by cl ...