fuel additives MERCEDES-BENZ C-CLASS 1999 Owners Manual

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 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
persons and no luggage,
• do not exceed 2/3 of maximum accelerator pedal positi on, 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 average of both the Research (R) octane number an d 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 components. 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
the use of only quality gasoline containing additives that prevent the build up of carbon deposits. After an extended
period of using fuels without such additives, carbon deposit s 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.


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