Mercedes-Benz S-Class Operator's Manual page 324

Refueling
322
use a sponge and cold water to clean it. DEF
residues crystallize after time and
contaminate the affected surfaces.
! DEF is not a fuel additive and must not be
added to the fuel tank. If DEF is added to
the fuel tank, this can lead to engine
damage.
i
If you are adding between maintenance
intervals, add approximately 1 gallon (3.8 l)
of DEF to the DEF tank. One gallon (3.8 l)
of DEF is approximately 2 DEF refill bottles.
Then, have the DEF supply checked and
filled completely if necessary. For this
purpose, Mercedes-Benz recommends a
qualified specialist workshop.
Further information on DEF (
The filler neck for DEF is located under the
"Minispare" emergency spare wheel in the
trunk floor.
X
Switch off the ignition.
X
Open the trunk.
X
Lift up the trunk floor (
X
Turn the "Minispare" emergency spare
wheel fastening in the direction of the
arrow and remove it.
X
Remove the "Minispare" emergency spare
wheel.
Y page 527).
Y page 436).
I n f o r ma t i o n P r o v i d e d b y :
X
Turn DEF cap : counter-clockwise and
remove it.
X
Turn DEF filler cap ; counter-clockwise
and open it.
Filler cap ; is secured with a plastic strap.
X
Unscrew the covering cap from DEF refill
bottle =.
X
Place DEF refill bottle = on the filler neck
as shown and screw on clockwise hand-
tight.
! Only screw on the DEF refill bottle hand-
tight. It could otherwise be damaged.