Engine Oils; Brake Fluid; Premium Unleaded Gasoline; Fuel Requirements - Mercedes-Benz 420 SEL 1989 Owner's Manual

Engine Oils

Engine oils are specifically tested for
their suitability in our engines. There­
fore, use only engine oils recom­
mended by us. Information on recom­
mended brands is available at your
authorized MERCEDES-BENZ dealer.

Brake Fluid

During vehicle operation, the boiling
point of the brake fluid is continuously
reduced through the absorption of
moisture from the atmosphere. Under
extremely hard operating conditions,
this moisture content can lead to the
formation of bubbles in the system
thus reducing the system's efficiency.
The brake fluid must therefore be
replaced annually, preferably in the
spring.
It is recommended to use only brake
fluid approved by MERCEDES-BENZ.
Your authorized MERCEDES-BENZ
dealer will provide you with additional
information.

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 par­
tially with unleaded regular and fill
up with premium unleaded as soon
as possible,
• avoid full throttle driving and ab­
rupt 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 % of maximum
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 91 min. It is an aver­
age 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 oxy­
genates such as Ethanol, MTBE, IPA,
IBA and TBA can be used provided
the ratio of any one of these oxy­
genates to gasoline does not
exceed 10%.
The ratio of Methanol to gasoline
must not exceed 3% plus additional
cosolvents.
Using mixtures of Ethanol and
Methanol is not allowed. MTBE may,
however, be added up to 15%.
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..
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