Yes, premium gasoline can be used in a generator if it meets the engine manufacturer’s fuel specification, but it usually provides no advantage. Most portable generators are designed for regular unleaded gasoline at the minimum octane stated in the manual.
Higher octane does not contain more usable energy and does not make a low-compression generator produce more power. Freshness, approved ethanol content and correct storage have a much larger effect on reliable starting.
What octane does a generator need?
Use the minimum Anti-Knock Index, or AKI, printed in the owner’s manual. Generac currently specifies at least 87 octane for its portable generators. Honda specifies a pump octane rating of 86 or higher for its generators.
Premium fuel is typically 91 to 93 AKI in the United States. It is safe only if it also meets the generator’s limits for ethanol and other additives.
When higher octane helps
Higher octane resists abnormal combustion. It is useful when an engine is specifically designed for it or when the manufacturer calls for a higher rating under certain conditions.
It will not fix stale fuel, a dirty carburetor, incorrect choke use, a clogged filter, weak ignition or excessive load. If the engine knocks on the specified fuel, stop and diagnose the cause rather than masking it with a more expensive grade.
Premium does not mean ethanol-free
Fuel grade and ethanol content are separate. Premium gasoline may contain up to 10% ethanol, while some stations sell ethanol-free regular or midgrade fuel.
Check the pump label. Do not use E15 or E85 in a conventional portable generator that is limited to E10.
Best fuel practice for a generator
- Use clean, fresh unleaded gasoline at or above the required octane.
- Stay within the manufacturer’s ethanol limit.
- Buy fuel in quantities you will rotate while fresh.
- Use stabilizer only as directed and only with fresh fuel.
- Follow the carburetor and tank procedure for storage.
- Never refuel a running or hot generator.
Bottom line
Premium gas normally will not harm a compatible generator, but it is rarely worth the extra cost. Use the manual’s minimum octane, keep ethanol within limits and focus on fresh fuel and correct storage.
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