MERCEDES-BENZ C350S 2008 W204 Owner's Manual

320 Operation
Driving instructions
Emission control
Certain systems of the engine and the
emission control system serve to keep the
toxic components of the exhaust gases
within permissible limits required by law.
These systems will function properly only
when maintained strictly according to fac-
tory specifications. Any adjustments on
the engine should, therefore, be carried
out only by qualified Mercedes-Benz Cen-
ter authorized technicians.
Engine adjustments should not be altered
in any way. The specified service proce-
dures must be carried out regularly accord-
ing to Mercedes-Benz servicing
requirements. For details please refer to
the Maintenance Booklet.
Warning!G
As with any vehicle, do not idle, park or op-
erate this vehicle in areas where combusti-
ble materials such as grass, hay or leaves
can come into contact with the hot exhaust
system, as these materials could be ignited
and cause a vehicle fire.
Warning!G
Inhalation of exhaust gas is hazardous to
your health. All exhaust gas contains carbon
monoxide (CO), and inhaling it can cause un-
consciousness and possible death.
Do not run the engine in confined areas
(such as a garage) which are not properly
ventilated. If you think that exhaust gas
fumes are entering the vehicle while driving,
have the cause determined and corrected
immediately. If you must drive under these
conditions, drive only with at least one win-
dow fully open at all times.

321 Operation
Driving instructions
Coolant temperature
During severe operating conditions,
e.g. stop-and-go traffic, the coolant tem-
perature may rise to approximately 248°F
(120°C).
The engine should not be operated with
the coolant temperature over 248°F
(120°C). Doing so may cause serious en-
gine damage which is not covered by the
Mercedes-Benz Limited Warranty.
Warning!G

Driving when your engine is badly over-
heated can cause some fluids, which
may have leaked into the engine com-
partment, to catch fire. You could be se-
riously burned.

Steam from an overheated engine can
cause serious burns and can occur just
by opening the hood. Stay away from
the engine if you see or hear steam com-
ing from it.
Stop the vehicle in a safe location away from
other traffic. Turn off the engine, get out of
the vehicle and do not stand near the vehicle
until the engine has cooled down.

322 Operation
At the gas station
Refueling
The fuel filler flap is located on the
right-hand side of the vehicle towards the
rear. Locking and unlocking the vehicle
with the SmartKey or the SmartKey with
KEYLESS-GO* (Canada only) automatically
locks and unlocks the fuel filler flap.1To open fuel filler flap
2To insert fuel filler cap
3Holder
Warning!G
Gasoline is highly flammable and poisonous.
It burns violently and can cause serious per-
sonal injury.
Never allow sparks, flame or smoking mate-
rials near gasoline!
Turn off the engine before refueling.
Whenever you are around gasoline, avoid in-
haling fumes and any skin or clothing con-
tact. Extinguish all smoking materials.
Direct skin contact with fuels and the inha-
lation of fuel vapors can damage your
health.
Warning!G
C 300/C 300 4MATIC/C 300 4MATIC Sport
and 300 Sport (with automatic transmis-
sion*):
Flexible Fuel Vehicles (identified by a label
reading Premium gasoline or E85 only! on
fuel filler flap):
Ethanol fuel (E85) and its vapors are highly
flammable, poisonous and burn easily. Etha-
nol fuel can cause serious injuries if ignited
or if you come into contact with it or inhale
fumes of it. Avoid inhalation of ethanol
fumes and skin contact with ethanol. Extin-
guish all open flames before refueling. Never
smoke or create sparks close to ethanol.
iIn case that the central locking system does
not release the fuel filler flap, or the opening
mechanism is clamping, notify Roadside Assis-
tance or an authorized Mercedes-Benz Center.
iOnly use premium unleaded gasoline with a
minimum Posted Octane Rating of 91 (average
of 96 RON / 86 MON). Information on gasoline
quality can normally be found on the fuel pump.
C 300/C 300 4MATIC/C 300 4MATIC Sport and
300 Sport (with automatic transmission*):
Flexible Fuel Vehicles are identified by a label
reading Premium gasoline or E85 only! on the
fuel filler flap.

323 Operation
At the gas station
Turn off the engine.
Vehicles with automatic transmission*:
Move the gear selector lever to
positionP (
page 140).
Remove the SmartKey from the starter
switch.
Vehicles with SmartKey with
KEYLESS-GO*:
Turn off the engine by pressing the
KEYLESS-GO* button once.
Open the driver’s door (this puts
the starter switch in position0,
same as with the SmartKey re-
moved from the starter switch). The
driver’s door then can be closed
again.
Open the fuel filler flap by pushing at
the point indicated by arrow 1.The fuel filler flap springs open.
Turn the fuel cap counterclockwise and
hold on to it until possible pressure is
released.
Take off the fuel filler cap and set it in
the direction of arrow 2 and place it
into holder 4 located on the inside of
the fuel filler flap.
To prevent fuel vapors from escaping
into open air, fully insert filler nozzle
unit.
Only fill your tank until the filler nozzle
unit cuts out – do not top off or over-
fill.
Replace the fuel cap by turning it clock-
wise until it audibly engages.
Close the fuel filler flap.
You should hear the latch close shut.
For more information on gasoline or E85, see
“Premium unleaded gasoline” (
page 481) or
the Factory Approved Service Products
pamphlet (USA only) in your vehicle literature
portfolio, or contact an authorized
Mercedes-Benz Center.
Warning!G
Overfilling of the fuel tank may create pres-
sure in the system which could cause a gas
discharge. This could cause the gas to spray
back out when removing the fuel pump noz-
zle, which could cause personal injury.
iMake sure to close the fuel filler flap before
locking your vehicle as the flap locking pin pre-
vents closing after you have locked the vehicle.
iLeaving the engine running and the fuel cap
open can cause the yellow engine malfunction
indicator lamp ± to illuminate.
For more information, see the “Practical hints”
section (
page 378).

324 Operation
At the gas station
Check regularly and before a long trip
1Coolant level
2Brake fluid
3Windshield washer and headlamp
cleaning system*Windshield washer system and head-
lamp cleaning system*
For more information on refilling the wash-
er reservoir, see “Windshield washer sys-
tem and headlamp cleaning system*”
(
page 330).
Coolant
For more information on coolant, see
“Coolant level” (
page 329) and see “Fu-
els, coolants, lubricants, etc.”
(
page 476).
Brake fluid
For information on brake fluid, see “Brake
fluid” (
page 480).Engine oil level
For more information on engine oil, see
“Engine oil” (
page 327).
Vehicle lighting
Check function and cleanliness. For more
information on replacing light bulbs, see
“Replacing bulbs” (
page 430).
For more information, see “Lighting”
(
page 108).
Tire inflation pressure
For information on tire inflation pressure,
see “Checking tire inflation pressure”
(
page 341).iOpening the hood (page 325).!If you find that the brake fluid in the brake
fluid reservoir has fallen to the minimum mark or
below, have the brake system checked for brake
pad thickness and leaks immediately. Notify an
authorized Mercedes-Benz Center immediately.
Do not add brake fluid as this will not solve the
problem. For more information, see “Practical
hints” (
page 376) and (page 400).

325 Operation
Engine compartment
Engine compartment
Hood
Opening
Warning!G
Do not pull the release lever while the vehi-
cle is in motion. Otherwise the hood could
be forced open by passing air flow.
This could cause the hood to come loose
and injure you and/or others.
Warning!G
If you see flames or smoke coming from the
engine compartment, or if the coolant tem-
perature gauge indicates that the engine is
overheated, do not open the hood. Move
away from vehicle and do not open the hood
until the engine has cooled down. If neces-
sary, call the fire department.
Warning!G
You could be injured when the hood is open
– even when the engine is turned off.
Parts of the engine can become very hot. To
prevent burns, let the engine cool off com-
pletely before touching any components on
the vehicle. Comply with all relevant safety
precautions.
Warning!G
To help prevent personal injury, stay clear of
moving parts when the hood is open and the
engine is running.
The radiator fan may continue to run for ap-
proximately 30 seconds or even restart af-
ter the engine has been turned off. Stay
clear of fan blades.
Warning!G
The engine is equipped with a transistorized
ignition system. Because of the high voltage
it is dangerous to touch any components (ig-
nition coils, spark plug sockets, diagnostic
socket) of the ignition system

with the engine running

while starting the engine

if ignition is “on” and the engine is
cranked manually

326 Operation
Engine compartment
The hood lock release lever is located to
the left of the steering wheel under the
dashboard.
1Release lever
Pull release lever 1 downwards.
The hood is unlocked.2Lever for opening the hood
Push lever2 under the hood upwards.
Pull up on the hood and then release it.
The hood will be automatically held
open at shoulder height by gas-filled
struts. Closing
Let the hood drop from a height of ap-
proximately 1 ft (30 cm).
The hood will lock audibly.
Check to make sure the hood is fully
closed.
If you can raise the hood at a point
above the headlamps, then it is not
properly closed. Open it again and let it
drop with somewhat greater force.
!To avoid damage to the windshield wipers or
hood, never open the hood if the wiper arms are
folded forward away from the windshield.
Warning!G
When closing the hood, use extreme caution
not to catch hands or fingers.
Be careful that you do not close the hood on
anyone.
Make sure the hood is securely engaged be-
fore driving off. Do not continue driving if the
hood can no longer engage after an acci-
dent, for example. The hood could otherwise
come loose while the vehicle is in motion
and endanger you and/or others.

327 Operation
Engine compartment
Engine oil
The amount of oil your engine needs will
depend on a number of factors, including
driving style. Higher oil consumption can
occur when

the vehicle is new

the vehicle is driven frequently at
higher engine speeds
Engine oil consumption checks should only
be made after the vehicle break-in period.Notes about checking engine oil level
When checking the oil level

the vehicle must be parked on level
ground

with the engine at operating tempera-
ture, the vehicle must have been
stationary for at least 5 minutes with
the engine turned off

with the engine not at operating tem-
perature yet, the vehicle must have
been stationary for at least 30 minutes
with the engine turned offChecking engine oil level with the oil
dipstick
To check the engine oil level with the oil
dipstick, do the following:
Open the hood (page 325).
1Oil dipstick
2Upper mark
3Lower mark
Pull out oil dipstick1.
Wipe oil dipstick1 clean.
Fully insert oil dipstick1 into the dip-
stick guide tube.
!Do not use any special lubricant additives,
as these may damage the drive assemblies. Us-
ing special additives not approved by
Mercedes-Benz may cause damage not covered
by the Mercedes-Benz Limited Warranty.
More information on this subject is available at
any Mercedes-Benz Center.


328 Operation
Engine compartment
Pull out oil dipstick1 again after ap-
proximately 5 seconds to obtain accu-
rate reading.
The oil level is correct when it is between
lower mark3 (min.) and upper mark2
(max.) of the oil dipstick.
If necessary, add engine oil.
For adding engine oil (
page 328).
For more information on engine oil, see the
“Technical data” section (
page 476) and
(
page 480).
For more information on messages in the
multifunction display concerning engine
oil, see the “Practical hints” section
(
page 387).Adding engine oil
1Filler cap
Unscrew filler cap1 from filler neck.
Add engine oil as required. Be careful
not to overfill with oil.
Be careful not to spill any oil when adding.
Avoid environmental damage caused by oil
entering the ground or water.
Screw filler cap1 back on filler neck.
For more information on engine oil, see the
“Technical data” section (
page 476) and
(
page 480).
Transmission fluid level
The transmission fluid level does not need
to be checked. If you notice transmission
fluid loss or gear shifting malfunctions,
have an authorized Mercedes-Benz Center
check the transmission.
iThe filling quantity between the upper and
lower marks on the oil dipstick is approximately
2.1 US qt. (2.0 l).
!Only use approved engine oils and oil filters
required for vehicles with Maintenance System.
For a listing of approved engine oils and oil fil-
ters, refer to the Factory Approved Service Prod-
ucts pamphlet (USA only) in your vehicle
literature portfolio, or contact an authorized
Mercedes-Benz Center.
Using engine oils and oil filters of specification
other than those expressly required for the Main-
tenance System, or changing of oil and oil filter
at change intervals longer than those called for
by the Maintenance System will result in engine
or emission control system damage not covered
by the Mercedes-Benz Limited Warranty.
!Excess oil must be siphoned or drained off.
It will cause damage to the engine and emission
control system not covered by the
Mercedes-Benz Limited Warranty.


329 Operation
Engine compartment
Coolant level
The engine coolant is a mixture of water
and anticorrosion/antifreeze. To check
the coolant level, the vehicle must be
parked on level ground and the engine
must be cool.
The coolant expansion tank is located on
the passenger side of the engine compart-
ment.
1Cap
2Coolant expansion tank
3Fluid level bridgeUsing a rag, turn cap1 slowly approx-
imately a half-turn counterclockwise to
release any excess pressure.
Continue turning the cap1 counter-
clockwise and remove it.
The coolant level is correct if the level

for cold coolant: reaches the white
marking (plastic bridge)3 inside the
coolant expansion tank2

for warm coolant: is approximately
0.6 in (1.5 cm) higher
Add coolant as required.
Replace and tighten cap1.
For more information on coolant, see the
“Technical data” section (
page 484).
Warning!G
In order to avoid potentially serious burns:

Use extreme caution when opening the
hood if there are any signs of steam or
coolant leaking from the cooling system,
or if the coolant temperature gauge indi-
cates that the coolant is overheated.

Do not remove pressure cap on coolant
reservoir if coolant temperature is
above 158°F (70°C). Allow engine to
cool down before removing cap. The
coolant reservoir contains hot fluid and
is under pressure.

Using a rag, slowly open the cap approx-
imately a half-turn to relieve excess
pressure. If opened immediately, scald-
ing hot fluid and steam will be blown out
under pressure.

Do not spill antifreeze on hot engine
parts. Antifreeze contains ethylene gly-
col which may burn if it comes into con-
tact with hot engine parts.