MERCEDES-BENZ R320 2008 W251 Owner's Manual

350 Operation
Driving instructions
Emission control
Certain engine systems serve to keep the
toxic components of the exhaust gases
within permissible legal limits.
These systems, of course, will function
properly only when maintained strictly
according to factory specifications.
Any adjustments on the engine should
therefore be carried out only by qualified
Mercedes-Benz Light Truck Center
authorized technicians.
Engine adjustments should not be altered
in any way. Moreover, the specified service
jobs must be carried out regularly accord-
ing to Mercedes-Benz servicing require-
ments. For details refer to the
Maintenance Booklet.Coolant temperature
During severe operating conditions and
stop-and-go city traffic, the coolant
temperature may rise to approximately
248°F (120°C).
The engine should not be operated
with the coolant temperature above
248°F (120°C). Doing so may cause seri-
ous engine damage which is not covered
by the Mercedes-Benz Limited Warranty.
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.

351 Operation
Driving instructions
Warning!G

Driving when your engine is overheated
can cause some fluids which may have
leaked into the engine compartment to
catch fire. You could be seriously
burned.

Steam from an overheated engine can
cause serious burns and can occur just
by opening the engine hood. Stay away
from the engine if you see or hear steam
coming from it.
Turn off the engine, get out of the vehicle
and do not stand near the vehicle until the
engine has cooled down.

352 Operation
At the gas station
Refueling
The fuel filler flap is located on the
right-hand side of the vehicle towards the
rear. Locking/unlocking the vehicle with
the SmartKey or the SmartKey with
KEYLESS-GO* automatically
locks/unlocks the fuel filler flap.
Turn off the engine

by turning the SmartKey to
position0 (
page 39). Remove the
SmartKey from the starter switch.

by pressing the KEYLESS-GO*
start/stop button (
page 41).
Open the driver’s door (with the
driver’s door open, starter switch is
now in position 0, same as
SmartKey removed from starter
switch).
Warning!G
Gasoline and diesel fuels are highly flamma-
ble and poisonous. They burn violently and
can cause serious personal injury.
Never allow sparks, flame or smoking mate-
rials near gasoline or diesel fuel!
Turn off the engine before refueling.
Whenever you are around gasoline or diesel
fuel, avoid inhaling fumes and skin or cloth-
ing contact, extinguish all smoking materi-
als.
Direct skin contact with gasoline or diesel
fuels and the inhalation of gasoline or diesel
fuel vapors are damaging to your health.
Warning!G
Do not fill diesel tanks with gasoline. Do not
mix diesel fuel with gasoline. Otherwise the
fuel system and engine could be damaged.
In addition, the vehicle could catch fire.
!Damage resulting from mixing gasoline with
diesel fuel is not covered by the Mercedes-Benz
Limited Warranty.
!Diesel engine: When filling the diesel fuel
tank using fuel containers, place a filling filter, a
suede cloth or a clean flannel cloth as a filter.
Otherwise, particles from the fuel container
could clog the fuel lines and/or the diesel
injection system.
iIn case the central locking system does not
release the fuel filler flap, see “Fuel filler flap”
(
page 475).

353 Operation
At the gas station
Briefly push on fuel filler flap at the
position indicated the arrow.
The fuel filler flap opens slightly.
Open the fuel filler flap completely.
Turn the fuel cap to the counterclock-
wise and hold on to it until possible
pressure is released.
Take off the fuel cap.
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 overfill.
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.
!The fuel filler cap is tethered to the fuel filler
neck. Do not drop the cap. It could damage the
vehicle paint finish.
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
nozzle, which could cause personal injury.
iLeaving the engine running and the fuel cap
open can cause the yellow fuel tank reserve
warning lamp to flash and the? malfunction
indicator lamp (USA only) or the± malfunc-
tion indicator lamp (Canada only) comes on.
For more information, see “Practical hints”
(
page 418).
iGasoline engine:
Only use premium unleaded gasoline with a min-
imum Posted Octane Rating of 91 (average of
96 RON/86 MON). Information on gasoline
quality can normally be found on the fuel pump.
Please contact gas station personnel in case
labels on the pump cannot be found.
For more information on gasoline, see “Premium
unleaded gasoline (gasoline engine)”
(
page 539), see “Fuel requirements”
(
page 540), and the Factory Approved Service
Products pamphlet (USA only) or contact an
authorized Mercedes-Benz Light Truck Center.
iDiesel engine:
Only use commercially available vehicular
ULTRA-LOW SULFUR HIGHWAY DIESEL FUEL
(15 ppm SULFUR MAXIMUM). Information on
diesel quality can normally be found on the fuel
pump. Please contact gas station personnel in
case labels on the pump cannot be found.
For more information on diesel fuels, refer to the
Factory Approved Service Products pamphlet
(USA only) or contact an authorized
Mercedes-Benz Light Truck Center.


354 Operation
At the gas station
Low outside temperatures
(diesel engine)
To prevent malfunctions, diesel fuel with
improved cold flow characteristics is of-
fered in the winter months. Check with
your fuel retailer.Check regularly and before a long trip
Open the hood (page 356).
Example illustration R 350 4MATIC
1Coolant level
2Brake fluid
3Windshield washer system and
headlamp cleaning system*
iDiesel engine:
If you have driven the vehicle until the tank was
empty, the fuel system needs to be bled
(
page 502).
!Diesel engine:
The engine is more susceptible to wear and
damage if you use

marine diesel fuel

heating oil

additives
The exhaust aftertreatment device will be
seriously damaged if you use

LOW SULFUR HIGHWAY DIESEL FUEL
(500 ppm SULFUR MAXIMUM)

any other diesel fuel with a sulfur content of
above 15 ppm
The use of such non-approved fuels and/or
special additives is not covered by the
Mercedes-Benz Limited Warranty.
!Do not fill the tank with gasoline. Do not
blend diesel fuel with gasoline or kerosine. The
fuel system and engine will otherwise be dam-
aged, which is not covered by the
Mercedes-Benz Limited Warranty.


355 Operation
At the gas station
Engine oil level
For more information on engine oil, see
“Engine oil” (
page 358).
Coolant
For normal replenishing, use water (pota-
ble water quality). For more information,
see “Coolant level” (
page 360) and
“Fuels, coolants, lubricants, etc.”
(
page 536).
Brake fluidWindshield/rear window washer
system and headlamp cleaning
system*
For more information on refilling the wash-
er reservoir, see “Windshield/rear window
washer system and headlamp cleaning
system*” (
page 362).
Vehicle lighting
Check function and cleanliness. For infor-
mation on replacing light bulbs, see “Re-
placing bulbs” (
page 480).
For more information, see “Exterior lamp
switch” (
page 143).
Tire inflation pressure
For more information, see “Checking tire
inflation pressure” (
page 373).
!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. Contact an
authorized Mercedes-Benz Light Truck Center
immediately. Do not add brake fluid as this will
not solve the problem. For more information, see
“Brake fluid” (
page 539).

356 Operation
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 display indicates that the engine is
overheated, do not open the hood. Move
away from the vehicle and do not open the
hood until the engine has cooled.
If necessary, 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 of 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
approximately 30 seconds or may even
restart after the engine has been turned off.
Stay clear of fan blades.
Warning!G
Vehicles with gasoline engine:
The engine is equipped with a transistor-
ized ignition system. Because of the high
voltage it is dangerous to touch any compo-
nents (ignition 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
turned manually

357 Operation
Engine compartment
The hood lock release lever is located in
the driver’s footwell.
1Hood lock release lever
Pull release lever1 downwards.
The hood is unlocked. Handle2 pro-
trudes slightly from the radiator grille.
If not, lift the hood slightly.2Handle for opening the hood
Press and hold handle2.
The hood is unlocked.
Pull up on the hood in direction of
arrow and then release it.
The hood will be automatically held
open at shoulder height by gas-filled
struts.
Warning!G
Vehicles with diesel engine:
The engine is equipped with a high-voltage
electronic control unit for the injection
system. Because of the high voltage it is
dangerous to touch any components of the
injection system (injectors, electrical wires)

with the engine running

while starting the engine

when the ignition is switched on
!To avoid damage to the windshield wipers or
hood, never open the hood if the wiper arms are
folded forward away from the windshield.

358 Operation
Engine compartment
Closing
Let the hood drop from a height of
approximately 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.
Engine oil
The amount of oil your engine needs will
depend on a number of factors, including
driving style. Increased 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.Checking engine oil level
When checking the oil level

the vehicle must be parked on level
ground

the vehicle must have been stationary
for at least 5 minutes with the engine
turned off
Example illustration R 350 4MATIC
1Oil dipstick
2Upper mark
3Lower mark
Open the hood (page 356).
Pull out oil dipstick1.
Warning!G
When closing the hood, use extreme caution
not to catch hand or fingers. Be careful that
you do not close the hood on anyone.
Make sure the hood is securely engaged be-
fore driving. Do not continue driving if the
hood can no longer engage after an accident
for example. The hood could otherwise
come loose while the vehicle is in motion
and injure you and/or others.
!Do not use any special lubricant additives,
as these may damage the drive assemblies.
Using 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 Light Truck Center.

359 Operation
Engine compartment
Wipe oil dipstick 1 clean.
Fully insert oil dipstick1 into the
dipstick guide tube.
Pull out oil dipstick1 again after
approximately 3 seconds to obtain
accurate reading.
The oil level is correct when it is between
lower mark 3 (min.) and upper mark 2
(max.) of the oil dipstick.
If necessary, add engine oil.
For more information on engine oil, see
“Technical data” section (
page 536) and
(
page 538).
For information on messages in the multi-
function display concerning engine oil, see
the “Practical hints” section (
page 451).Adding engine oil
Example illustration R 350 4MATIC
1Filler cap
Unscrew filler cap1 from filler neck.
Add engine oil as required. Be careful
not to overfill with oil.
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
filters, refer to the Factory Approved Service
Products pamphlet (USA only) in your vehicle
literature portfolio, or contact an authorized
Mercedes-Benz Light Truck Center.
Using engine oils and oil filters of specification
other than those expressly required for the
Maintenance 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.