Mercedes-Benz SLK-Class 2007 Owners Manual - Manual (Page 448)

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Technical data
Fuels, coolants, lubricants, etc.
Fuel requirements
Only use premium unleaded fuel:
ț The octane number (posted at the
pump) must be 91 min. It is an
average of both the Research Octane
Number (RON) and the Motor Octane
Number (MON): (RON+MON)/2. This is
also known as the ANTI-KNOCK INDEX.
Unleaded gasoline containing oxygenates
such as ethanol, IPA, IBA, and TBA can
be used provided the ratio of any one of
these oxygenates to gasoline does not
exceed 10%; MTBE not to exceed 15%.
The ratio of methanol to gasoline must not
exceed 3% plus additional cosolvents.
Using mixtures of ethanol and methanol is
not allowed. Gasohol, which contains
10% ethanol and 90% unleaded gasoline,
can be used.
These blends must also meet all other fuel
requirements, such as resistance to spark
knock, boiling range, vapor pressure, etc.
Gasoline additives
A major concern among engine manufac-
turers is carbon build-up caused by gaso-
line. Mercedes-Benz only recommends
only the use of quality gasoline containing
additives that prevent the build-up of
carbon deposits.
After an extended period of using fuels
without such additives, carbon deposits
can build up, especially on the intake
valves and in the combustion area, leading
to engine performance problems such as:
ț Warm-up hesitation
ț Unstable idle
ț Knocking/pinging
ț Misfire
ț Power loss
In areas where carbon deposits may be
encountered due to lack of availability of
gasolines which contain these additives,
Mercedes-Benz recommends the use of
additives approved by us for use on
Mercedes-Benz vehicles. Refer to Factory
Approved Service Products pamphlet
(USA only) or contact an authorized
Mercedes-Benz Center for a listing of
approved product(s). Follow directions on
product label.
Do not blend other fuel additives with fuel.
This only results in unnecessary costs and
may be harmful to engine operation.
!
Damage or malfunction resulting from poor
fuel quality or from blending additional fuel
additives other than those tested and approved
by us for use on Mercedes-Benz vehicles are not
covered by the Mercedes-Benz Limited
Warranty.