• Every Honda generator is test-run at the factory; power output levels, engine speed, circuit breakers, Eco-Throttle, etc. are all evaluated. The oil is then extracted from the engine, but a tiny amount usually remains in the crankcase.
• The owner's manual has a maintenance schedule and it says to check the oil level before each use, and to change the oil after 1 month or 20 hours of use. Afterword, change it every 6 months or 100 hours of use. Many models incorporate a sequence of blinking LEDs to indicate the hours of use that have accumulated.
• Honda recommends using a petroleum-based oil (SAE 10W-30) but synthetic is acceptable. The only reason Honda recommends a petroleum-based oil is because that's the type of oil used when the emissions system is certified.
• Engineers have told me the key getting the most life out of any small gasoline engine is to (a) change the oil per the schedule. (b) Use a good quality SAE 10W30 oil.
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I work for Honda, but the preceding is my opinion alone.
Robert@Honda