Honda EU20i Owner's Manual page 20

Check the fuel level.
2.
If the fuel level is low, refuel the fuel tank until the level as specified.
After refueling, tighten the fuel filler cap securely.
Use automotive unleaded gasoline with a Research Octane Number of
91 or higher (a Pump Octane Number of 86 or higher).
Never use stale or contaminated gasoline or an oil/gasoline mixture.
Avoid getting dirt or water in the fuel tank.
Gasoline is extremely flammable and is explosive under certain
conditions.
Refuel in a well ventilated area with the engine stopped. Do not
smoke or allow flames or sparks in the area where the engine is
refueled or where gasoline is stored.
Do not overfill the fuel tank (there should be no fuel above the
upper limit mark). After refueling, make sure the fuel filler cap is
closed properly and securely.
Be careful not to spill fuel when refueling. Spilled fuel or fuel vapor
may ignite. If any fuel is spilled, make sure the area is dry before
starting the engine.
Avoid repeated or prolonged contact with skin or breathing of
vapor.
KEEP OUT OF REACH OF CHILDREN.
FUEL FILLER CAP
18
OPEN
UPPER LIMIT MARK