See also:

Removing the towing eye
  Loosen the towing eye and unscrew it.   Attach cover 1 to the bumper and press until it engages.   Place the towing eye in the vehicle tool kit. ...

Please bear the following in mind
Resetting service interval display If the qualified specialist workshop, e.g. a Mercedes-Benz Center, carried out the maintenance work, the service interval display will be reset. Further info ...

Additives
Do not use any additives in the engine oil. This could damage the engine. ...