fuel pressure MERCEDES-BENZ R320 2008 W251 Owner's Manual

Contents
Oxidation catalyst
(diesel engine).............................. 349
Emission control .......................... 350
Coolant temperature .................... 350
At the gas station .............................. 352
Refueling ...................................... 352
Check regularly and before a
long trip........................................ 354
Engine compartment ......................... 356
Hood ............................................ 356
Engine oil ..................................... 358
Transmission fluid level ................ 360
Coolant level ................................ 360
Windshield/rear window washer
system and headlamp cleaning
system* ....................................... 362
Tires and wheels ................................ 363
Important guidelines .................... 363
Tire care and maintenance........... 364
Direction of rotation ..................... 365
Loading the vehicle ...................... 366
Recommended tire inflation
pressure ....................................... 371
Checking tire inflation pressure ... 373
Tire labeling.................................. 384
Load identification ....................... 388DOT, Tire Identification Number
(TIN) .............................................. 388
Maximum tire load ........................ 390
Maximum tire inflation pressure ... 390
Uniform Tire Quality Grading
Standards (U.S. vehicles) .............. 391
Tire ply material ............................ 393
Tire and loading terminology......... 393
Rotating tires ................................ 396
Winter driving ..................................... 398
Winter tires ................................... 398
Snow chains.................................. 399
Maintenance....................................... 400
Maintenance service indicator
message ....................................... 400
Calling up the maintenance
service indicator display ............... 402
Resetting the maintenance
service indicator ........................... 402
Vehicle care........................................ 403
Cleaning and care of the vehicle ... 403
Practical hints.................................. 413
What to do if … ................................... 414
Lamps in instrument cluster ......... 414
Lamp in center console ................ 425
Vehicle status messages in the
multifunction display .................... 427
Where will I find ...? ............................ 467
First aid kit.................................... 467
Vehicle tool kit.............................. 467
Spare wheel .................................. 471
Unlocking / locking in an emergency .. 474
Unlocking the vehicle ................... 474
Locking the vehicle ....................... 475
Fuel filler flap ................................ 475
Resetting activated head restraints.... 477
Vehicles without Rear Seat
Entertainment Package................. 477
Vehicles with Rear Seat
Entertainment Package*............... 478
Replacing SmartKey batteries ............ 479
Replacing bulbs .................................. 480
Bulbs............................................. 480
Replacing bulbs for front lamps .... 483
Replacing bulbs for rear lamps ..... 487

23 At a glance
Exterior view
ItemPage
1Tailgate119
Power tailgate*119
Cargo compartment

Loading instructions

Cargo tie-down rings

Hooks

Expanding

Cover blind

Cargo net*
289
290
291
292
299
301
Vehicle tool kit467
Spare wheel471
2Rear window defroster207
3Rear lamps481
4Fuel filler flap352
Refueling352
Fuel353,
540
ItemPage
5Exterior rear view mirrors
Adjusting48
Auto-dimming rear view
mirrors*203
Power folding*204
6Towing eye bolt467
Installing towing eye bolt515
7Tires and wheels363,
529
Checking tire inflation
pressure373
General information363
Flat tire492
Spare wheel471
8Hood
Opening356
Engine oil358
Coolant360
ItemPage
9Windshield wipers59
Wiper blades, replacing489
Wiper blades, cleaning409
aWindshield
Cleaning with wiper fluid61
Cleaning409
bPower tilt/sliding sunroof*248
Panorama roof with power
tilt/sliding panel*252
cDoors
Locking and unlocking110
Opening and closing118
Locking/unlocking in an
emergency474
dFront lamps480
eHeadlamp cleaning system*203

339 Operation
Driving instructions
Driving instructions
Drive sensibly – save fuel
Fuel consumption, to a great extent,
depends on driving habits and operating
conditions.
To save fuel you should:

Keep tires at the recommended
inflation pressures.

Remove unnecessary loads.

Remove carriers when not in use.

Allow engine to warm up under low
load use.

Avoid frequent acceleration and
deceleration.

Have all maintenance work performed
at the intervals specified in the
Maintenance Booklet and as required
by the Maintenance System. Contact
an authorized Mercedes-Benz Light
Truck Center.
Fuel consumption is also increased by
driving in cold weather, in stop-and-go
traffic, on short trips and in hilly area.
Drinking and drivingPedals
Warning!G
Drinking and driving and/or taking drugs
and driving are a very dangerous combina-
tion. Even a small amount of alcohol or
drugs can affect your reflexes, perceptions
and judgment.
The possibility of a serious or even fatal
accident are greatly increased when you
drink or take drugs and drive.
Do not drink or take drugs and drive or allow
anyone to drive who has been drinking or
taking drugs.
Warning!G
Make sure that absolutely no objects are ob-
structing the pedal’s range of movement.
Keep the driver’s footwell clear of all obsta-
cles. If there are any floormats or carpets in
the footwell, make sure the pedals still have
sufficient clearance.
During sudden driving or braking maneu-
vers, the objects could get caught between
the pedals. You could then no longer brake
or accelerate. This could lead to accidents
and injury.

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.


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).

366 Operation
Tires and wheels
Loading the vehicle
Two labels on your vehicle show how much
weight it may properly carry.
1) The Tire and Loading Information
placard can be found on the driver’s
door B-pillar. This placard tells you im-
portant information about the number
of people that can be in the vehicle and
the total weight that can be carried in
the vehicle. It also contains information
on the proper size and recommended
tire inflation pressures for the original
equipment tires on your vehicle.2) The certification label, also found on
the driver’s door B-pillar. It tells you
about the gross weight capacity of your
vehicle, called the Gross Vehicle
Weight Rating (GVWR). The GVWR
includes the weight of the vehicle, all
occupants, fuel and cargo. The certifi-
cation label also tells you about the
front and rear axle weight capacity,
called the Gross Axle Weight Rating
(GAWR). The GAWR is the total allow-
able weight that can be carried by a
single axle (front or rear). Never exceed
the GVWR or GAWR for either the front
axle or rear axle.
1Driver’s door B-pillar
Following is a discussion on how to work
with the information contained on the Tire
and Loading Information placard with
regards to loading your vehicle.
iSpare wheels may be mounted against the
direction of rotation (spinning) even with a
unidirectional tire for temporary use only until
the regular drive wheel has been repaired or
replaced. Always observe and follow applicable
temporary use restrictions and speed limitations
indicated on the spare wheel.

371 Operation
Tires and wheels
Recommended tire inflation pressure
Your vehicle is equipped with the Tire and
Loading Information placard located on
the driver’s door B-pillar (
page 366).
The tire inflation pressure should be
checked regularly and should only be ad-
justed on cold tires. The tires can be con-
sidered cold if the vehicle has been parked
for at least 3 hours or driven less than
1 mile (1.6 km).
Follow recommended cold tire inflation
pressures listed on Tire and Loading
Information placard on the driver’s door
B-pillar.
Keeping the tires properly inflated
provides the best handling, tread life and
riding comfort.
In addition to the Tire and Loading
Information placard on the driver’s door
B-pillar, also consult the tire inflation
pressure label (if available) on the fuel filler
flap (
page 352) for any additional infor-mation pertaining to special driving situa-
tions. For more information, see
“Important notes on tire inflation
pressure” (
page 372).
1Tire and Loading Information placard
with recommended cold tire inflation
pressuresWarning!G
Follow recommended tire inflation
pressures.
Do not underinflate tires. Underinflated tires
wear excessively and/or unevenly,
adversely affect handling and fuel economy,
and are more likely to fail from being over-
heated.
Do not overinflate tires. Overinflated tires
can adversely affect handling and ride
comfort, wear unevenly, increase stopping
distance, and result in sudden deflation
(blowout) because they are more likely to
become punctured or damaged by road
debris, potholes etc.
Do not overload the tires by exceeding the
specified load limit as indicated on the Tire
and Loading Information placard on the driv-
er’s door B-pillar. Overloading the tires can
overheat them, possibly causing a blowout.
Overloading the tires can also result in
handling or steering problems, or brake
failure.
iData shown on Tire and Loading Information
placard example are for illustration purposes
only. Tire data are specific to each vehicle and
may vary from data shown in the following
illustration. Refer to Tire and Loading
Information placard on vehicle for actual data
specific to your vehicle.

372 Operation
Tires and wheels
The Tire and Loading Information placard
lists the recommended cold tire inflation
pressures for maximum loaded vehicle
weight. The tire inflation pressures listed
apply to the tires installed as original
equipment.
Important notes on tire inflation
pressure
Tire temperature and tire inflation pressure
are also increased while driving, depending
on the driving speed and the tire load.If you will be driving your vehicle at high
speeds of 100 mph (160 km/h) or higher,
where it is legal and conditions allow,
consult the tire inflation pressure label on
the inside of the fuel filler flap (if available)
on how to adjust the cold tire inflation
pressure. If you do not adjust the tire infla-
tion pressure, excessive heat can build up
and result in sudden tire failure.
If your vehicle is not equipped with the tire
inflation pressure label on the inside of the
fuel filler flap, contact an authorized
Mercedes-Benz Light Truck Center for
proper tire inflation pressure.Make sure to readjust the tire inflation
pressure for normal driving speeds. You
should wait until the tires are cold before
adjusting the tire inflation pressure.
Some vehicles may have supplemental tire
inflation pressure information for vehicle
loads less than the maximum loaded vehi-
cle condition. If such information is provid-
ed, it can be found on the tire inflation
pressure label located on the inside of the
fuel filler flap (
page 352).
Tire inflation pressure changes by approxi-
mately 1.5 psi (0.1 bar) per 18°F (10°C) of
air temperature change. Keep this in mind
when checking tire inflation pressure
where the temperature is different from
the outside temperature.Warning!G
If the tire inflation pressure drops
repeatedly:

Check the tires for punctures from
foreign objects.

Check to see whether air is leaking from
the valves or from around the rim.
iDriving comfort may be reduced when the
tire inflation pressure is adjusted to the value for
speeds above 100 mph (160 km/h) as specified
on the tire inflation pressure label located on the
inside of the fuel filler flap.

373 Operation
Tires and wheels
Checking tire inflation pressure
Regularly check the tire inflation pressure
at least once a month.
Check and adjust the tire inflation
pressure when the tires are cold. The tires
can be considered cold if the vehicle has
been parked for at least 3 hours or driven
less than 1 mile (1.6 km).
If you check the tire inflation pressure
when the tires are warm (the vehicle has
been driven for several miles or sitting less
than 3 hours), the reading will be
approximately 4 psi (0.3 bar) higher than
the cold reading. This is normal. Do not let
air out to match the specified cold tire
inflation pressure. Otherwise, the tire will
be underinflated.Checking tire inflation pressure
manually
Follow the steps below to achieve correct
tire inflation pressure:
Remove the cap from the valve on one
tire.
Firmly press a tire gauge onto the
valve.
Read tire inflation pressure on tire
gauge and check against the recom-
mended tire inflation pressure on the
Tire and Loading Information placard
on the driver’s door B-pillar
(
page 366) or, if available, the tire in-
flation pressure label on the inside of
the fuel filler flap. If necessary, add air
to achieve the recommended tire
inflation pressure.
Warning!G
Follow recommended tire inflation
pressures.
Do not underinflate tires. Underinflated tires
wear excessively and/or unevenly,
adversely affect handling and fuel economy,
and are more likely to fail from being over-
heated.
Do not overinflate tires. Overinflated tires
can adversely affect handling and ride
comfort, wear unevenly, increase stopping
distance, and result in sudden deflation
(blowout) because they are more likely to
become punctured or damaged by road
debris, potholes etc.
Do not overload the tires by exceeding the
specified load limit as indicated on the Tire
and Loading Information placard on the
driver’s door B-pillar. Overloading the tires
can overheat them, possibly causing a
blowout. Overloading the tires can also
result in handling or steering problems, or
brake failure.


374 Operation
Tires and wheels
Install the valve cap.
Repeat this procedure for each tire.
Run Flat Indicator (Canada only)
While the vehicle is being driven, the Run
Flat Indicator monitors the set tire inflation
pressures by evaluating each wheel’s rota-
tional speed. This allows the system to de-
tect a significant loss of pressure in a tire.
If a wheel’s rotational speed changes due
to falling tire inflation pressure, you will
see a corresponding warning message in
the multifunction display.The Run Flat Indicator may function in a re-
stricted manner or with a delay

if snow chains are mounted to the
vehicle

in presence of ice and snow

if you are driving on a loose surface
(e.g. sand or gravel)

if you are driving in a very sporty
manner (involving rapid acceleration or
high speeds in curves)
iIf you have overfilled the tire, release tire in-
flation pressure by pushing the metal stem of the
valve with e.g. a tip of a pen. Then recheck the
tire inflation pressure with the tire gauge.Warning!G
When the multifunction display shows the
message
Tire Pressure Check Tires,
one or more of your tires is significantly un-
derinflated. You should stop and check your
tires as soon as possible, and inflate them to
the proper tire inflation pressure as in-
dicated on the vehicle’s Tire and Loading
Information placard or, if available, on the
tire inflation pressure label. Driving on a sig-
nificantly underinflated tire causes the tire
to overheat and can lead to tire failure. Un-
derinflation also reduces fuel efficiency and
tire tread life, and may affect the vehicle’s
handling and stopping ability. Each tire, in-
cluding the spare, should be checked
monthly when cold and set to the recom-
mended tire inflation pressure as specified
on the Tire and Loading Information placard
(
page 366) or on the tire inflation pres-
sure label located on the inside of the fuel
filler flap (
page 352).