DEF
Important safety notes
Comply with the important safety notes for service products when handling DEF .
DEF is a water-soluble fluid for the exhaust gas aftertreatment of diesel engines. It is: • not poisonous • colorless and odorless • not flammable When you open the DEF container, small amounts of ammonia vapor may be released
Ammonia vapors have a pungent odor and are particularly irritating to the skin, to mucous membranes and to the eyes. You may experience a burning sensation in your eyes, nose and throat. Coughing and watering of the eyes are possible.
Do not inhale ammonia vapors. Fill the DEF tank only in well-ventilated areas.
Low outside temperatures
DEF freezes at a temperature of
approximately 12 
(-11
). The vehicle is
delivered from the factory equipped with a
DEF preheating system. Winter operation can
thus be guaranteed even at temperatures
below 12 
(-11
).
Additives
Only use DEF in accordance with ISO 22241. Do not use additives with DEF and do not dilute DEF with water. This may destroy the BlueTEC exhaust gas aftertreatment system.
Purity
Impurities in DEF (e.g. due to other
service products, cleaning agents or dust)
lead to:
• increased emission values
• damage to the catalytic converter
• engine damage
• malfunctions in the BlueTEC exhaust gas
aftertreatment system
Filling capacities
See also:
Instrument cluster
Displays and controls
1 Speedometer with segments
2 Multifunction display
3 Tachometer
4 Coolant temperature
5 Fuel gauge
6 Instrument cluster lighting brightness control: turn clockwise or
c ...
Off-road driving systems
4MATIC (permanent four-wheel drive)
If you fail to adapt your driving style, 4MATIC
can neither reduce the risk of accident nor
override the laws of physics. 4MATIC cannot
take account of road, we ...
Winter driving
General no
DANGER
If the exhaust pipe is blocked or adequate
ventilation is not possible, poisonous gases
such as carbon monoxide (CO) may enter the
vehicle. This is the case, e.g. if the vehicle ...