Mercedes-Benz C-Class Convertible 2021 Operator's Manual page 393

If you have accidentally refueled with the
wrong fuel:
do not switch the ignition on.
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Consult a qualified specialist workshop.
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If the available fuel is not sufficiently low in sul‐
fur, this can produce unpleasant odors.
Only refuel with fuel that has at least the octane
number specified in the information label in the
fuel filler flap ( page 141).
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If you want maximum engine output: only
refuel with unleaded premium grade gasoline
with an octane number of at least 91 AKI/
95 RON.
As a temporary measure, if the recommended
fuel is not available, you may also refuel with
unleaded regular gasoline with at least 87 AKI/
91 RON. This may reduce engine output and
increase fuel consumption.
Never refuel using gasoline with an even lower
RON.
* NOTE Premature wear through unleaded
regular gasoline
Unleaded regular gasoline can cause the
engine to wear more quickly and impair lon‐
gevity and performance.
If unleaded premium grade gasoline is
unavailable and you have to refuel using
unleaded regular gasoline:
Only fill the fuel tank to half full with
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unleaded regular gasoline and refill as
soon as possible with unleaded pre‐
mium grade gasoline.
Do not drive at the maximum design
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speed.
Avoid sudden acceleration engine
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speeds over 3000 rpm.
Further information on fuel is available at the fol‐
lowing locations:
at a gas station
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at a qualified specialist workshop
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on the https://www.mbusa.com (USA only)
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Technical data 391
Notes on additives in gasoline
Observe the notes on operating fluids
( page 389).
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* NOTE Damage from use of unsuitable
additives
Even small amounts of the wrong additive
may lead to malfunctions occurring.
Only add cleaning additives recommen‐
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ded by Mercedes-Benz to the fuel.
Mercedes-Benz recommends that you use
brand-name fuels with additives.
In some countries, the fuel available may not
have sufficient additives. Residue could build up
in the fuel injection system as a result. In this
case, in consultation with an authorized
Mercedes-Benz Center, mix the fuel with the
cleaning additive recommended by Mercedes-
Benz. Observe the notes and mixing ratios indi‐
cated on the tank.