Mercedes-Benz 1998 SL 500 Operator's Manual page 149

Premium Unleaded Gasoline
Caution!
To maintain the engine's durability and
performance, premium unleaded
gasoline must be used. If premium
unleaded is not available and low
octane fuel is used, follow these
precautions:
•
have the fuel tank filled only
partially with unleaded regular
and fill up with premium un
leaded 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 persons and no luggage,
• 2
do not exceed / of maximum
3
accelerator pedal position, if the
vehicle is fully loaded or operating
in mountainous terrain.
Fuel Requirements
Use only Premium unleaded meeting
ASTM standard D 439:
The octane number (posted at the
pump) must be 91min. 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 ANTI-KNOCK INDEX.
Unleaded gasoline containing
oxygenates such as Ethanol, I PA, 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
manufacturers is carbon build up
caused by gasoline. Mercedes-Benz
recommends to use only 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:
•
warm-up hesitation,
•
unstable idle,
•
knocking/pinging,
•
misfire,
•
power loss.
Do not blend other specific fuel
additives with fuel. They only result in
unnecessary cost, and may be harmful
to the engine operation.
Damage or malfunctions resulting
from poor fuel quality or from
blending specific fuel additives are not
covered by the Mercedes-Benz
Limited Warranty.
149