How long does gasoline last without a stabilizer?

Untreated gasoline starts degrading in 30 to 60 days. Ethanol-blended fuel (E10, which is most fuel sold in the United States) degrades faster because ethanol absorbs moisture from the air, which can cause phase separation. In a sealed, full container stored in a cool place, untreated gasoline may last three to six months before causing starting problems. In a partially filled container with air space, degradation accelerates.

Can fuel stabilizer fix gas that has already gone bad?

Most stabilizers cannot. STA-BIL Storage is designed to prevent degradation, not reverse it. PRI-G and Star Tron both claim the ability to restore aged fuel, and independent testing has confirmed that PRI-G can return stale gasoline to usable condition in many cases. However, no product can reverse phase separation once ethanol and water have fully separated from the gasoline. Once you see layers in the container, the fuel should be disposed of properly.

Should I use stabilizer in my generator even if I run it monthly?

Yes. Running a generator monthly exercises the engine, but the fuel in the tank and fuel lines is still aging. A stabilizer prevents gum and varnish buildup in the carburetor and fuel system between runs. This is especially important if you only run the generator for a few minutes each month, because the fuel sitting in the carburetor bowl is the fuel most likely to varnish.

Does fuel stabilizer work with ethanol-free gas?

Yes. All four stabilizers in this comparison work with both ethanol-blended and ethanol-free gasoline. Ethanol-free gas lasts longer on its own, but it still degrades through oxidation. A stabilizer extends its usable life further. If you can find ethanol-free fuel in your area, combining it with a stabilizer gives you the longest possible storage window.

How much fuel stabilizer do I need for a five-gallon gas can?

It depends on the product. STA-BIL Storage requires 2 ounces for 5 gallons (24-month protection). Sea Foam requires 5 ounces for 5 gallons (1 ounce per gallon for storage). PRI-G requires less than half a teaspoon for 5 gallons due to its 1:2000 concentration ratio. Star Tron Concentrate requires about 0.3 ounces for 5 gallons. Always follow the dosing instructions on your specific bottle, and always add stabilizer to fresh fuel, not fuel that has already been sitting.

Home Gear Reviews Best Fuel Stabilizers

Roundup Comparison · Energy

Best fuel stabilizers for stored generators.

Four fuel stabilizers compared on storage duration, cost per treated gallon, ethanol protection, and whether they can bring old fuel back to life. If you own a generator that sits for months between uses, the fuel stabilizer you choose determines whether it starts when you need it.

Last verified September 2026.

Quick picks

Four stabilizers, four different jobs.

Each pick wins for a different storage scenario. Most households need the first one. Serious fuel reserve keepers need the second. The last two earn their place for specific situations.

Affiliate disclosure: New World Survival earns a small commission on purchases made through the links below, at no cost to you. We only recommend gear we would put in our own kit. Commission never decides a recommendation.

Our Pick

STA-BIL Storage

32 oz · Treats 80 gal · 24 months

The most widely available fuel stabilizer in the country. Two years of protection, available at every hardware store, and the standard that most generator manufacturers recommend. The right answer for most households.

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Best Long-Term

PRI-G

32 oz · Treats 500 gal · 3+ years

Super concentrated at a 1:2000 ratio, cheapest per treated gallon, and the only stabilizer here that can genuinely restore old fuel. Annual re-treatment extends storage indefinitely. The serious fuel reserve choice.

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Best for Ethanol

Star Tron Enzyme

32 oz · Treats 512 gal · 2 years

Enzyme technology disperses water at the molecular level, preventing the phase separation that ruins ethanol-blended fuel. Works in both gasoline and diesel. Can rejuvenate fuel that has started to go stale.

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Most Versatile

Sea Foam SF-16

16 oz · Treats 16 gal · 2 years

Fuel stabilizer, injector cleaner, upper cylinder lubricant, and oil treatment in one can. Not the cheapest per gallon, but the most useful can to keep in the garage if you maintain multiple engines.

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Side by side

The full field, compared.

Stabilizer	Bottle	Treats	Storage	Cost/Gal	Restores Old Fuel	Fuel Types	Award
STA-BIL Storage	32 oz	80 gal	24 months	~$0.15	No	Gasoline	Our Pick
PRI-G	32 oz	500 gal	3+ years	~$0.05	Yes	Gasoline	Best Long-Term
Star Tron Enzyme	32 oz	512 gal	2 years	~$0.05	Partial	Gas + Diesel	Best for Ethanol
Sea Foam SF-16	16 oz	16 gal	2 years	~$0.63	No	Gas + Diesel	Most Versatile

Cost per gallon based on typical retail pricing as of September 2026. Actual prices vary by retailer.

How we chose

The question is not if, but which.

Untreated gasoline degrades in 30 to 60 days. Ethanol-blended fuel, which accounts for the vast majority of gasoline sold in the United States, degrades faster because ethanol absorbs atmospheric moisture, which eventually causes the ethanol and water to separate from the gasoline entirely. This is called phase separation, and no stabilizer can reverse it once it happens. Prevention is the only strategy.

We evaluated four stabilizers on the criteria that matter for emergency generator storage: how long they extend fuel life, how much they cost per treated gallon, whether they handle ethanol-blended fuel, and whether they can do anything for fuel that has already started to degrade. We also factored in availability, because a stabilizer you cannot find at a local store when you need it is not a solution.

STA-BIL earns Our Pick because it delivers reliable 24-month protection at a reasonable cost and is stocked at nearly every hardware store, auto parts shop, and big-box retailer in the country. For most households with one generator and a few gas cans, it is the right answer.

PRI-G earns Best Long-Term because its 1:2000 concentration ratio makes it the cheapest per treated gallon by a wide margin, its storage window extends beyond three years with annual re-treatment, and independent testing has confirmed its ability to restore mildly degraded fuel. It is the choice for serious fuel reserves.

Star Tron and Sea Foam each fill a specific niche. Star Tron's enzyme technology handles water dispersion at the molecular level, making it the strongest defense against ethanol-related problems. Sea Foam does more than stabilize: the same can cleans injectors, lubricates upper cylinders, and treats crankcase oil, making it the most useful single product for households that maintain multiple small engines.

Best practices

How to store fuel so it actually works.

The stabilizer matters less than the process. Add stabilizer at the gas station, immediately after filling the container with fresh fuel. Never add stabilizer to fuel that has already been sitting. Run the generator for five minutes after adding stabilized fuel so the treated fuel reaches the carburetor and fuel lines.

Keep containers 95 percent full to minimize the air space where condensation forms. Store in a cool, dry, well-ventilated area away from direct sunlight. Use approved fuel containers with tight-fitting caps. Label each container with the date of purchase and the stabilizer used.

Rotate your fuel. Use the oldest stored fuel first and replace it with fresh treated fuel. Even stabilized fuel performs best when rotated every 12 to 18 months. If you follow the STA-BIL dosing and store properly, that 24-month window is real. If you follow the PRI-G annual re-treatment protocol, you can extend that considerably.

For a full guide on fuel containers, capacity planning, and rotation schedules, see our approved gas cans review.

For generator selection, sizing, and safe operation, visit the Energy self-reliance section.