FS 55, FS 55 C, FS 55 R, FS 55 RC
English
24
Removing the metal cutting 
attachment
N Block the drive shaft.
N Unscrew the mounting nut 
clockwise.
N Take the parts off the shaft – do not 
remove the thrust plate (5).
This engine is certified to operate on 
unleaded gasoline and the STIHL two-
stroke engine oil at a mix ratio of 50:1.
Your engine requires a mixture of high-
quality gasoline and quality two-stroke 
air cooled engine oil.
Use mid-grade unleaded gasoline with a 
minimum octane rating of 89 (R+M/2). If 
the octane rating of the mid-grade 
gasoline in your area is lower, use 
premium unleaded fuel.
Fuel with a lower octane rating may 
increase engine temperatures. This, in 
turn, increases the risk of piston seizure 
and damage to the engine.
The chemical composition of the fuel is 
also important. Some fuel additives not 
only detrimentally affect elastomers 
(carburetor diaphragms, oil seals, fuel 
lines, etc.), but magnesium castings and 
catalytic converters as well. This could 
cause running problems or even 
damage the engine. For this reason 
STIHL recommends that you use only 
high-quality unleaded gasoline!
Gasoline with an ethanol content of 
more than 10% can cause running 
problems and major damage in engines 
with a manually adjustable carburetor 
and should not be used in such engines.
Engines equipped with M-Tronic can be 
run on gasoline with an ethanol content 
of up to 25% (E25).
Use only STIHL two-stroke engine oil or 
equivalent high-quality two-stroke 
engine oils that are designed for use 
only in air cooled two-cycle engines.
We recommend STIHL HP Ultra 2-Cycle 
Engine Oil since it is specially 
formulated for use in STIHL engines.
Do not use BIA or TCW rated (two-
stroke water cooled) mix oils or other 
mix oils that state they are for use in both 
water cooled and air cooled engines 
(e.g., outboard motors, snowmobiles, 
chain saws, mopeds, etc.).
Take care when handling gasoline. 
Avoid direct contact with the skin and 
avoid inhaling fuel vapor. When filling at 
the pump, first remove the canister from 
your vehicle and place the canister on 
the ground before filling. Do not fill fuel 
canisters that are sitting in or on a 
vehicle.
The canister should be kept tightly 
closed in order to avoid any moisture 
getting into the mixture.
The machine‘s fuel tank and the canister 
in which fuel mix is stored should be 
cleaned as necessary.
Fuel mix ages
Only mix sufficient fuel for a few days 
work, not to exceed 3 months of storage. 
Store in approved fuel-canisters only. 
When mixing, pour oil into the canister 
first, and then add gasoline. Close the 
canister and shake it vigorously by hand 
to ensure proper mixing of the oil with 
the fuel.
Fuel