To function properly, BlueTEC exhaust gas aftertreatment must be operated with the reducing agent DEF. Adding DEF is one of the tasks performed during maintenance. Under normal operating conditions, a tank of DEF lasts until the next service due date.

When the DEF supply has almost run out, the Check Additive See Operator's Manual message is shown in the multifunction display.

When the DEF supply sinks to a minimum level, the Remaining Starts: 16 message is shown in the multifunction display.

When the Remaining Starts: 16 message is shown in the multifunction display, you can start the engine 16 more times. If DEF is not added, it is then not possible to start the engine again. Fill the DEF tank with about 1 gal (3.8 l) DEF or have the DEF tank refilled at a qualified specialist workshop.

Use the special DEF refill bottle when filling between maintenance intervals. Contact an authorized Mercedes-Benz Center with any questions or, if necessary, contact Roadside Assistance.

Further information about BlueTEC exhaust gas aftertreatment and DEF is available at any authorized Mercedes-Benz Center.