Premium Unleaded Gasoline; Fuel Requirements; Gasoline Additives - Mercedes-Benz 2003 S 430 Operator's Manual

Technical data
Fuels, coolants, lubricants etc.

Premium unleaded gasoline

!
To maintain the engine's durability and
performance, premium unleaded gaso-
line must be used. If premium unleaded
gasoline is not available and low octane
fuel is used, follow these precautions:
Have the fuel tank only partially
filled with unleaded regular and fill
up with premium unleaded as soon
as possible.
Avoid full throttle driving and abrupt
acceleration.
Do not exceed an engine speed of
3000 rpm if the vehicle is loaded
with a light load such as two per-
sons and no luggage.
Do not exceed 2/3 of maximum ac-
celerator pedal position if the vehi-
cle is fully loaded or operating in
mountainous terrain.
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Fuel requirements

Use only premium unleaded gasoline
meeting ASTM standard D 439:
The octane number (posted at the
pump) must be 91 min (93 for S 600).
It is an average of both the Research
(R) octane number and the Motor (M)
octane number: (R+M)/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 must not exceed 15%.
The ratio of methanol to gasoline must not
exceed 3% plus additional co-solvents.
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 recommends only the
use of quality gasoline containing additives
that prevent the build-up of carbon depos-
its.
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 en-
gine performance problems such as:
Warm-up hesitation
Unstable idle
Knocking/pinging
Misfire
Power loss
Do not blend any specific fuel additives
with fuel. This only results in unnecessary
cost and may be harmful to the engine op-
eration.