Can I Leave Fuel in My Generator?
Ever filled up your generator thinking, “Too easy, I’ll leave it ready for next time,” only to wonder months later if you’ve accidentally created a ticking time bomb of gunk and engine grief? You’re not alone. The short answer: yes, you can leave fuel in your generator—but only for a short time and with precautions. Otherwise, it can go off quicker than milk in the summer sun.
Let’s dig into the how, why, and what to do if you forgot to empty the tank after last storm season.
Answering "Can I leave fuel in my generator" and Other Community Questions
How long can I leave fuel in my generator
If you're only storing your generator for a few weeks, you're probably fine—if you use a fuel stabiliser. Anything longer, and it’s worth taking extra steps.
Understanding the Lifespan of Gasoline in Your Generator's Tank
Petrol in your generator can start breaking down in as little as 30 days, especially in the heat. Over time, it forms gums and varnish, which clog your engine’s insides. In cooler temps, you might stretch that lifespan a little—but not much.
The Aussie climate, particularly up north, doesn’t help. Scorching days and humid nights can speed up fuel breakdown even faster than you’d expect.
The Accelerated Breakdown of Ethanol-Blended Fuels
Got E10 in the tank? You might be in for a world of trouble. Ethanol attracts moisture, and when water gets into the mix, fuel separation can occur. That leads to corrosion, sludge, and a very grumpy generator come start-up time.
Even in temperate regions like Melbourne or Sydney, ethanol-blended fuel doesn’t last long in a sealed tank—let alone one exposed to hot sheds or caravan storage spaces.
Symptoms of bad gas in generator
Not sure if your fuel’s gone bad? Your generator might already be giving you the clues.
Recognising Common Signs of Fuel Degradation
Signs of stale fuel aren’t always obvious at first. You might notice:
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Trouble starting the generator
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Rough or surging engine performance
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Unusual exhaust smells
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Higher fuel consumption than usual
If your generator ran perfectly before and now splutters like it’s caught the flu, old fuel might be the culprit.
The Dangers of Varnish and Sludge Build-up
Varnish sounds harmless, but in a generator, it’s nasty. It forms a sticky coating inside the carburettor and fuel lines, blocking proper fuel flow. Sludge is even worse—it can settle at the bottom of the tank, coat the filter, and choke your generator completely.
Leave it long enough, and you're looking at costly repairs or even a full replacement.
What to Do with Your Generator If Its Fuel is Left Inside
So you left petrol in the tank. Now what?
Fuel stabiliser for generator
This little additive can be a lifesaver.
How Fuel Stabilisers Prevent Breakdown and Protect Your Generator
Fuel stabilisers work by slowing oxidation and preventing the formation of gums and varnish. They’re especially handy for Aussie conditions where heat can wreck fuel in record time.
Top picks include:
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STA-BIL: A popular option with solid performance.
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Lucas Fuel Stabilizer: Great for both petrol and diesel.
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Penrite Fuel Stabiliser: An Aussie-made choice that’s up to the job.
Proper Application of Stabiliser for Your Generator's Fuel
Here’s how to do it right:
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Add the stabiliser before filling the tank.
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Fill up with fresh fuel.
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Run the generator for 5–10 minutes to circulate the treated fuel through the system.
This keeps the entire fuel system protected—even if the generator sits unused for a few months.
How to remove gas from generator
If the fuel’s already been sitting a while, draining is your safest bet.
A Step-by-Step Guide to Safely Draining Your Generator's Fuel
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Turn off the generator and let it cool completely.
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Find the fuel shut-off valve and close it (if equipped).
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Disconnect the fuel line or open the drain plug (check your model’s manual).
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Catch the old fuel in a safe container—don’t just let it spill onto the ground.
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Start the generator and let it run until it stops, burning off any leftover fuel.
Always do this in a well-ventilated area, away from flames or sparks.
Best Practices for Disposing of Old or Contaminated Gas
Don’t pour it down the drain or onto the lawn.
Take the old fuel to your local hazardous waste disposal centre or council collection point. Many petrol stations and mechanics can also point you in the right direction.
Preparing Your Generator for Storage
Getting ready for a long break between uses? Don’t just switch it off and forget it.
Should I run generator out of gas before storage
Yes—especially if it’ll be unused for over 6 months. Letting it run dry prevents stale fuel from gumming up the works. It’s a simple step that saves headaches down the track.
If your generator has a fuel shut-off switch, use that while it's running. It burns through what’s in the carburettor, leaving it bone dry and clean.
What happens if a generator runs out of gas during the night
Letting your generator run out of fuel during use can damage it—particularly inverter models. Why? Because the engine may continue turning without proper fuel combustion, which can hurt the alternator and electronics.
If you expect an overnight run, top up beforehand or switch to a model with automatic shut-off.
Final thought? Leaving fuel in your generator isn’t the end of the world—if you do it right. But if you’ve let it sit too long or used dodgy fuel, don’t ignore the warning signs. A few small steps now can save you serious repairs (and headaches) later.
Let your generator rest easy—and fire up when you need it most.
You might also like:
- Can You Have a Generator Outside?
- Can You Run a Generator on a Covered Patio?
- How Do Small Generators Work?
- Is It Better to Store a Generator Full or Empty?
- Should Generators Be Kept Outside?
- Should You Leave a Generator on All Night?
- What Is the Australian Standard for Generators?
