Page 295 of 474

294 Operation
Engine compartment
Hood
Opening
1Hood lock release lever
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 the vehicle and do not open the 
hood until the engine has cooled. 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 
approximately 30 seconds or may even 
restart after 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 
(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 
     
        
        Page 297 of 474

296 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.Checking engine oil level with the 
control system (SLK 55 AMG only)
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 sta-
tionary for at least 5 minutes with the 
engine turned off.
with the engine not at operating tem-
perature, the vehicle must have been 
stationary for at least 30 minutes with 
the engine turned off.To check the engine oil level via the 
multifunction display, do the following:
Switch on the ignition (page 37).
The standard display appears in the 
multifunction display (
page 127).
Press buttonk orj on the mul-
tifunction steering wheel repeatedly 
until the following message appears in 
the multifunction display (
page 122):
!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 authorized Mercedes-Benz Center. 
     
        
        Page 298 of 474

297 Operation
Engine compartment
One of the following messages will 
subsequently appear in the multifunc-
tion display:
Engine Oil Level
OK
Add 1.0 qt. (Canada: 1.0 liter)
to reach max. oil level.
Add 1.5 qts. (Canada: 
1.5 liters)
to reach max. oil level.
Add 2.0 qts. (Canada: 
2.0 liters)
to reach max. oil level.
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).Other display messages
If the ignition is not switched on, the fol-
lowing message will appear:
Turn on ignition
to see engine oil level
.
Switch on the ignition (page 37).
If you see the message:
Observe
Waiting Time
If engine is at operating temperature, 
wait 5 minutes before repeating check 
procedure.
If engine is not at operating tempera-
ture yet, you must wait 30 minutes 
before checking oil.If you see the message:
Cannot check engine oil level
with engine on.
Turn off the engine.
If the engine is at operating tempera-
ture, wait 5 minutes before checking 
oil.
If the engine is not at operating 
temperature yet, you must wait 
30 minutes before checking oil.
iIf you want to interrupt the checking 
procedure, press buttonk orj on the 
multifunction steering wheel (
page 122).
iIf you want to interrupt the checking 
procedure, press buttonk orj on the 
multifunction steering wheel (
page 122). 
     
        
        Page 299 of 474

298 Operation
Engine compartment
If there is excess engine oil with the engine 
at normal operating temperature, the 
following message will appear:
Engine Oil Level
Reduce Oil Level
Have excess oil siphoned or drained 
off. Contact an authorized 
Mercedes-Benz Center.
For more information on messages in the 
display concerning engine oil, see the 
“Practical hints” section (
page 360).Checking engine oil level with the oil 
dipstick (SLK 280, SLK 350 only)
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, the vehicle must have been 
stationary for at least 30 minutes with 
the engine turned off.1Oil dipstick
2Upper (max) mark
3Lower (min) mark
To check the engine oil level with the oil 
dipstick, do the following:
Open the hood (page 294).
Pull out oil dipstick1.
Wipe oil dipstick1 clean.
Fully insert oil dipstick1 into the 
dipstick guide tube.
!Excess oil must be siphoned or drained off. 
It could cause damage to the engine and 
catalytic converter not covered by the 
Mercedes-Benz Limited Warranty. 
     
        
        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 340 of 474

339 Operation
Maintenance
Resetting the maintenance service 
indicator 
In the event that the maintenance service 
on your vehicle is not carried out by an 
authorized Mercedes-Benz Center, you can 
have the maintenance service indicator 
reset. The automotive maintenance facility 
carrying out the maintenance service will 
find the information for resetting the main-
tenance service indicator in the mainte-
nance-relevant literature for your vehicle. 
Such literature is available from any autho-
rized Mercedes-Benz Center or directly 
from Mercedes-Benz.iIf the battery is disconnected, the days of 
disconnection will not be included in the count 
shown by the maintenance service indicator. To 
arrive at the true maintenance service deadline, 
you will need to subtract these days from the 
days shown in the maintenance service indicator 
message or maintenance service indicator dis-
play.
Do not confuse the maintenance service indica-
tor with the engine oil level indicatorN.
iIf the maintenance service indicator was 
inadvertently reset, have an authorized 
Mercedes-Benz Center correct it.
Only reset if the proper maintenance service has 
been performed. Resetting the system without 
performing the proper maintenance service as 
called for by the maintenance service indicator 
will result in engine damage and/or other vehicle 
damage not covered by the Mercedes-Benz 
Limited Warranty. 
     
        
        Page 378 of 474
377 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
±Display Malfunction
Drive To WorkshopCertain electronic systems are un-
able to relay information to the con-
trol system. The following systems 
may have failed:
Coolant temperature display
Tachometer
Cruise control display
Have the electronic systems checked by an 
authorized Mercedes-Benz Center.
NCheck oil level
when next refueling
.
SLK 280 and SLK 350 only:
The engine oil level has dropped to 
a critical level.Check the engine oil level (page 296) and 
add engine oil as required (
page 299).
If you must add engine oil frequently, have 
the engine checked for possible leaks.