Honda EB4000 Owner's Manual page 21

Tool kit
The tools supplied are necessary for performing some periodic maintenance,
simple adjustments and repairs.
Always keep the kit with the generator.
Changing oil
Drain the oil while the engine is still warm to assure rapid and complete
draining.
1. Remove the drain plug and filler cap, and drain the oil. Retighten the plug
securely.
2. Refill with the recommended oil (see page 4) and check the level.
OIL FILLER CAP
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