Honda EB3500X Owner's Manual page 28

Occasionally you may hear 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.
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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 gasolines are being blended with alcohol or an ether compound to
increase the octane. These gasolines are collectively referred to as oxygenated
fuels. Some areas of the United States use oxygenated fuels to help meet
clean air standards.
If you use an oxygenated fuel, be sure its pump octane rating is 86 or higher.
Ethanol (ethyl or grain alcohol)
Gasoline containing more than 10% ethanol by volume may cause starting
and/or performance problems. Gasoline containing ethanol may be marketed
under the name "Gasohol".
Methanol (methyl or wood alcohol)
Gasoline containing methanol must contain cosolvents and corrosion inhibitors
to protect the fuel system. Gasoline containing more than 5% methanol by
volume may cause starting and/or performance problems and may damage
metal, rubber and plastic parts of your fuel system.
MTBE (methyl tertiary butyl ether)
You may use gasoline containing up to 15% MTBE by volume.
Before using an oxygenated fuel, try to confirm the fuel's contents. Some
states (provinces in Canada) require this information to be posted on the
pump. If you notice any undesirable operating symptoms, switch to a
conventional unleaded gasoline. Fuel system damage or performance problems
resulting from the use of an oxygenated fuel are not the responsibility of Honda
and are not covered under warranty.
(1
Oxygenated fuels can damage paint and plastic. Be careful
not to spill fuel when filling
your fuel tank. Damage caused by spilled fuel
is not covered under warranty.
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