Honda GL1800 2004 Owner's Manual page 222

Oxygenated Fuels
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 warranty.
Oxygenated fuels can damage paint and plastic. Be careful not to spill fuel when
filling the fuel tank. Wipe up any spills immediately.
Oxygenated f uels can damage paint and plastic. Damage caused by spilled f uel
is not covered by warranty.
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Technical Information