What Gasoline Should You Use in a Portable Generator?
By the Generator Size Calculator Team · Updated · 5 min read
Quick answer: One Honda generator manual says to use low-lead or unleaded automotive gasoline with a pump octane rating of 86 or higher. It forbids oil and gasoline mixtures and warns against dirty gasoline and gasoline substitutes. That manual does not address ethanol blends, so check yours for a limit. Fuel for a four-stroke generator is plain gasoline, and the oil goes in its own sump.
Your manual comes first. This page uses figures from one Honda generator manual (the EM1600X, EM1800X and EM2200X, with a GX140 engine). Other engines, and fuel-injected or inverter models, can behave differently, so check your own owner's manual.
The fuel to use
The Honda manual says to use low-lead or unleaded automotive gasoline with a pump octane rating of 86 or higher. Regular unleaded at most U.S. pumps is rated 87, so it meets that. Four-stroke generators like this one keep their oil in a separate sump, so the gasoline goes in plain, with no oil added. See the oil intervals in how often to change generator oil.
What not to use
- Oil and gasoline mixtures. The manual prohibits them. Two-stroke mixes are for two-stroke engines.
- Dirty gasoline. Dirt and water can clog the fuel system.
- Gasoline substitutes. The manual advises against them.
What the manual does not say
That Honda manual does not mention ethanol, E10 or gasohol, so it gives no blend limit. Other makers do list limits, and some engines tolerate ethanol blends better than others. Look in your own manual or on the fuel cap for the maximum ethanol blend and any minimum octane. If the manual lists a different octane, follow it.
Fueling tips
- Use fresh fuel. Gasoline that has sat for months can cause hard starts. Check your manual for storage advice.
- Refuel only when the generator is off and cool. See how to refuel a generator safely.
- Plan how much you need. See the fuel consumption calculator and propane vs gasoline generators.
See how much fuel an outage will use.
Run the generator outdoors, at least 20 feet from the home. Never in a garage or shed. Carbon monoxide has no smell or color. See how far a generator should be from your house.
Frequently asked questions
What gas does a portable generator use?
One Honda manual says low-lead or unleaded automotive gasoline with a pump octane rating of 86 or higher. Check your own manual.
Can I use regular 87 octane gas in a generator?
In that manual, 87 meets the 86 or higher requirement. Use what your manual lists.
Do I mix oil with the gas?
Not in a four-stroke generator. That manual prohibits oil and gasoline mixtures.
Can I use ethanol gas in a generator?
The Honda manual does not address it. Check your own manual for a maximum ethanol blend.
Can I use old gasoline?
Dirty or stale fuel can cause problems. The manual warns against dirty gasoline, so use fresh fuel.
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Sources: Honda owner's manual for the EM1600X, EM1800X and EM2200X generators (low-lead or unleaded automotive gasoline with pump octane 86 or higher; oil and gasoline mixtures, dirty gasoline and substitutes not recommended; ethanol not addressed). Remarks about 87-octane pumps and two-stroke mixes are general knowledge.