We recently tested our portable Honda generator; it wouldn’t start. The local repair shop discovered that the carburetor had failed due to corrosion — the kind of corrosion caused by the ethanol in gasoline. Newer engines will eventually become more tolerant of gasoline-ethanol blends, but older ones were never designed to be used with these fuels.
As a preventative treatment, this appears to be an effective product. It is advertised as preventing gum buildup and corrosion. Product documentation and instructions are clear and are featured in a nice readable font. It’s widely available from a variety of automotive parts stores.