Honda EM3800SX Owner's Manual page 31

Occasionally you may hear a light ''spark knock'' or ''pinging''
(metallic rapping noise) while operating under heavy loads. This is no
cause for concern.
If spark knock or pinging occurs at a steady engine speed, under
normal load, change brands of gasoline. If spark knock or pinging
persists, see an authorized Honda generator dealer.
Running the engine with persistent spark knock or pinging can cause
engine damage.
Running the engine with persistent spark knock or pinging is misuse,
and the Distributor's Limited Warranty does not cover parts damaged
by misuse.
Oxygenated Fuels
Some conventional gasolines are being blended with alcohol or an
ether compound. These gasolines are collectively referred to as
oxygenated fuels. To meet clean air standards, some areas of the
United States and Canada use oxygenated fuels to help reduce
emissions.
If you use an oxygenated fuel, be sure it is unleaded and meets the
minimum octane rating requirement.
Before using an oxygenated fuel, try to confirm the fuel's contents.
Some states/provinces require this information to be posted on the
pump.
The following are the EPA approved percentages of oxygenates:
ETHANOL
MTBE
METHANOL
If you notice any undesirable operating symptoms, try another service
station or switch to another brand of gasoline.
Fuel system damage or performance problems resulting from the use
of an oxygenated fuel containing more than the percentages of
oxygenates mentioned above are not covered under the Distributor's
Limited Warranty .
(ethyl or grain alcohol) 10% by volume
You may use gasoline containing up to 10% ethanol
by volume. Gasoline containing ethanol may be
marketed under the name ''Gasohol''.
(methyl tertiary butyl ether) 15% by volume
You may use gasoline containing up to 15% MTBE by
volume.
(methyl or wood alcohol) 5% by volume
You may use gasoline containing up to 5% methanol
by volume as long as it also contains cosolvents and
corrosion inhibitors to protect the fuel system.
Gasoline containing more than 5% methanol by
volume may cause starting and/or performance
problems. It may also damage metal, rubber, and
plastic parts of your fuel system.
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