Page 300 of 474

299 Operation
Engine compartment
Pull out oil dipstick1 again after 
approximately 3 seconds to obtain 
accurate reading.
The oil level is correct when it is be-
tween the lower (min) mark3 and 
upper (max) mark2 of oil dipstick1.
If necessary, add engine oil.
For adding engine oil, see “Adding 
engine oil” (
page 299).
For more information on engine oil, see 
“Fuels, coolants, lubricants, etc.” 
(
page 451).
For more information on messages in the 
multifunction display concerning engine 
oil, see the “Practical hints” section 
(
page 360).Adding engine oil
SLK 350 (example illustration)
1Filler cap
SLK 55 AMG
1Filler cap
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 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. 
     
        
        Page 301 of 474

300 Operation
Engine compartment
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 
“Technical data” (
page 451) and 
(
page 453).
Transmission fluid level*
Vehicles with automatic transmission*: 
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.
Coolant level
The engine coolant is a mixture of water 
and anticorrosion/antifreeze.
When checking the coolant level,
the vehicle must be parked on level 
ground
the coolant temperature must be 
below 158°F (70°C)
!Excess oil must be siphoned or drained off. 
It could cause damage to the engine and 
emission control system not covered by the 
Mercedes-Benz Limited Warranty.
Warning!G
In order to avoid any 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 1/2turn to relieve excess pres-
sure. If opened immediately, scalding 
hot fluid and steam will be blown out 
under pressure.
Do not spill antifreeze on hot engine 
parts. Antifreeze contains ethylene 
glycol which may burn if it comes into 
contact with hot engine parts. 
     
        
        Page 302 of 474

301 Operation
Engine compartment
The coolant expansion tank is located on 
the passenger side of the engine compart-
ment.
SLK 350 (example illustration)
1Coolant expansion tank
2Cap
3Marking bar in the expansion tank
Using a rag, turn cap2 slowly approx-
imately one half turn counterclockwise 
to release any excess pressure.
Continue turning cap2 counterclock-
wise and remove it.
The coolant level is correct if the level 
for cold coolant: reaches marking 
bar3 in expansion tank1
for warm coolant: is approximately 
0.6 in (1.5 cm) higher
Add coolant as required.
Replace and tighten cap2.
For more information on coolant, see 
“Coolants” (
page 456).Windshield washer system and 
headlamp cleaning system*
The windshield washer reservoir is located 
on the passenger side of the engine com-
partment.
SLK 350 (example illustration)
1Cap for windshield washer reservoir
Fluid for the windshield washer system 
and the headlamp cleaning system* is 
supplied from the windshield washer 
reservoir. It has a capacity of 
approximately 7.4 US qt (7 l). 
     
        
        Page 332 of 474

331 Operation
Tires and wheels
Tire and loading terminology
Accessory weight
The combined weight (in excess of those 
standard items which may be replaced) of 
automatic transmission, power steering, 
power brakes, power windows, power 
seats, radio, and heater, to the extent that 
these items are available as 
factory-installed equipment (whether 
installed or not).
Air pressure
The amount of air inside the tire pressing 
outward on each square inch of the tire. 
Air pressure is expressed in pounds per 
square inch (psi), or kilopascal (kPa), or 
bars.
Aspect ratio
Dimensional relationship between tire 
section height and section width 
expressed in percentage.Bar
Another metric unit for air pressure. There 
are 14.5038 pounds per square inch (psi) 
to 1 bar; there are 100 kilopascals (kPa) 
to 1 bar.
Bead
The tire bead contains steel wires wrapped 
by steel cords that hold the tire onto the 
rim.
Cold tire inflation pressure
Tire inflation pressure when your vehicle 
has been sitting for at least three hours or 
driven no more than 1 mile (1.6 km). 
Curb weight
The weight of a motor vehicle with stan-
dard equipment including the maximum 
capacity of fuel, oil, and coolant, and, if so 
equipped, air conditioning and additional 
optional equipment, but without passen-
gers and cargo.DOT (Department of Transportation)
A tire branding symbol which denotes the 
tire meets requirements of the 
U.S. Department of Transportation.
GAWR (G
ross Axle Weight Rating)
The GAWR is the maximum permissible 
axle weight. The gross vehicle weight on 
each axle must never exceed the GAWR for 
the front and rear axle indicated on the 
certification label located on the driver’s 
door B-pillar.
GVW (G
ross Vehicle Weight)
The GVW comprises the weight of the 
vehicle including fuel, tools, spare wheel, 
installed accessories, passengers and 
cargo and, if applicable, trailer tongue 
load. The GWV must never exceed the 
GWVR indicated on the certification label 
located on the driver’s door B-pillar. 
     
        
        Page 341 of 474

340 Operation
Vehicle care
Cleaning and care of vehicle
Regular and proper care will help to main-
tain the value of your vehicle. The best way 
to protect your vehicle from harmful envi-
ronmental influences is to wash it and use 
protective treatments regularly.
While in operation, even while parked, your 
vehicle is subjected to varying external in-
fluences which, if gone unchecked, can at-
tack the paintwork as well as the 
undercarriage and cause lasting damage.Such damage is caused not only by 
extreme and varying climatic conditions, 
but also by:
Air pollution
Road salt
Tar
Gravel and stone chipping
To avoid paint damage, you should imme-
diately remove:
Grease and oil
Fuel
Coolant
Brake fluid
Bird droppings
Insects
Tree resins, etc.
Frequent washing reduces and/or elimi-
nates the aggressiveness and potency of 
the above adverse influences.More frequent washings are necessary to 
deal with unfavorable conditions:
near the ocean
in industrial areas (smoke, exhaust 
emissions)
during winter operation
You should check your vehicle from time to 
time for stone chipping or other damage. 
Any damage should be repaired as soon as 
possible to prevent corrosion.
In doing so, do not neglect the underbody 
of the vehicle. A prerequisite for a 
thorough check is a washing of the under-
body followed by a thorough inspection. 
Damaged areas need to be 
re-undercoated.
Your vehicle has been treated at the 
factory with a wax-base rustproofing in the 
body cavities which will last for the lifetime 
of the vehicle. Post-production treatment 
is neither necessary nor recommended by 
Mercedes-Benz because of the possibility 
Warning!G
Many cleaning products can be hazardous. 
Some are poisonous, others are flammable. 
Always follow the instructions on the partic-
ular container. Always open your vehicle’s 
doors or windows when cleaning the inside.
Never use fluids or solvents that are not de-
signed for cleaning your vehicle.
Always lock away cleaning products and 
keep them out of reach of children. 
     
        
        Page 372 of 474
371 Practical hints
What to do if …
Symbol messages
Display symbolDisplay messagePossible cause/consequencePossible solution
ÊThis message will appear whenever 
the trunk lid is open.Close the trunk lid.
OYou are driving with the hood open.Risk of accident!
Stop the vehicle in a safe location or as soon 
as it is safe to do so.
Apply the parking brake (page 59).
Close the hood (page 294).
JYou are driving with one or more 
doors open.Close the doors.
•The cooling fan for the coolant is 
malfunctioning.Observe the coolant temperature display 
(
page 127).
If the coolant temperature is below 120°C, 
you may continue driving to the nearest 
specialist workshop.
Avoid heavy loads on the engine (e.g. by 
driving uphill) as well as stop-and-go traffic.
Have the fan replaced as soon as possible. 
     
        
        Page 375 of 474
374 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
•Coolant
Stop, turn engine 
off
.
The coolant is too hot.
Among other possible causes, 
the poly-V-belt could be broken.Stop the vehicle in a safe location or as soon as it is 
safe to do so.
Turn off the engine.
Apply the parking brake (page 59).
Check the poly-V-belt.
If it is broken:
Do not continue to drive. Otherwise, the engine will 
overheat due to an inoperative water pump which 
may result in damage to the engine. Contact an 
authorized Mercedes-Benz Center.
If it is intact:
Wait for the message to disappear before restarting 
the engine.
Doing otherwise could result in serious engine 
damage that is not covered by the Mercedes-Benz 
Limited Warranty.
(Continued on next page) 
     
        
        Page 376 of 474

375 Practical hints
What to do if …
During severe operating conditions, e.g. 
stop-and-go traffic, the coolant tempera-
ture may rise close to 248°F (120°C).
Display symbolDisplay messagePossible cause/consequencePossible solution
Observe the coolant temperature display 
(
page 127).
If the temperature rises again:
Contact an authorized Mercedes-Benz 
Center immediately.
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 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.
!The engine should not be operated with the 
coolant temperature above 248°F (120°C). 
Doing so may cause serious engine damage 
which is not covered by the Mercedes-Benz 
Limited Warranty.