Honda EG2500X Owner's Manual page 24

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.
-1 Running the engine with persistent spark knock or
pinging can cause engine damage.
Running the engine wilh 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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