Fuel Stabilizer Dosage Calculator

How to use this calculator

Enter the number of gallons you're treating, select your stabilizer brand (which sets the dose rate automatically), and choose your planned storage duration. For storage over 12 months, the calculator automatically recommends doubling the dose as most manufacturers advise. If your brand isn't listed, select "Custom rate" and enter the oz-per-gallon ratio from your product's label.

Dose rates by brand

Every stabilizer concentrates differently, so the right dose depends on the product. These are the manufacturers' standard storage rates. Double the dose for storage beyond 12 months.

Product	Standard dose	One 8-oz bottle treats	Best for
STA-BIL Storage (red)	1 oz per 2.5 gal	~20 gal	General storage, up to 24 months at double dose
STA-BIL 360 Protection	1 oz per 2.5 gal	~20 gal	Ethanol and moisture defense
Sea Foam Motor Treatment	1 oz per 1 gal	~8 gal	Carb cleaning plus short storage
PRI-G	1 oz per 16 gal	~128 gal	Bulk, long-term storage
Techron or generic	1 oz per 3 gal	~24 gal	Light stabilizing plus cleaning

In metric, STA-BIL's 1 oz per 2.5 gallons works out to about 3 mL of stabilizer per litre of fuel (30 mL treats 9.5 L). Canadian retailers such as Canadian Tire carry STA-BIL and Sea Foam; PRI-G is more of a specialty order.

Tips for success

• Add before filling. Add stabilizer to the container before filling with fuel, or immediately after, then run the engine for a few minutes to circulate treated fuel through the carburetor and fuel lines. Stabilizer in a can doesn't help the carburetor bowl.
• E10 degrades fast. Untreated regular gasoline (10% ethanol) begins to degrade in as little as 30 days. Ethanol absorbs moisture from the air and can phase-separate, leaving a corrosive water-ethanol layer at the bottom of the tank.
• Double-dose for 12+ months. For storage over 12 months, double the standard dose and use ethanol-free (E0) fuel if available. Ethanol-free gasoline stores significantly longer than E10 even with stabilizer.
• Rotate on schedule. Rotate stored fuel every 6–12 months by using it in your vehicle or equipment and replacing with fresh fuel and a fresh dose of stabilizer.
• Cool, dark storage. Store fuel in approved containers away from living spaces, ignition sources, and direct sunlight. Temperature swings accelerate fuel degradation even with stabilizer.

How fuel degrades during storage

• Oxidation. Gasoline reacts with oxygen in the air, forming gums and varnish deposits that clog carburetors, fuel injectors, and filters. This process begins within weeks in warm conditions.
• Ethanol phase separation. E10 gasoline absorbs moisture from ambient air. Once enough water accumulates, the ethanol-water mixture separates from the gasoline and sinks to the bottom. This layer is highly corrosive and won't burn properly in most engines.
• Light end evaporation. The most volatile, energy-rich components of gasoline evaporate first. Old gasoline is harder to start and produces less power than fresh fuel.
• Stabilizer mechanism. Fuel stabilizers work primarily as antioxidants; they interrupt the oxidation chain reaction that forms gums and varnish. They cannot prevent ethanol separation, which is why ethanol-free fuel is preferred for long-term storage.

Common mistakes

• Treating old fuel. Stabilizer does not reverse degradation that has already occurred. Always treat fresh fuel.
• Under-measuring for small batches. For batches under 2 gallons, use a marked medicine cup or syringe; eyeballing from a large bottle leads to underdosing.
• Skipping the engine run-through. After treating, run the engine 5–10 minutes so treated fuel reaches the carburetor bowl; untreated fuel left in carb bowls causes the worst varnish.
• Using Sea Foam for bulk storage. Sea Foam doses at 1 oz/gal, making it expensive for pure long-term storage. Switch to PRI-G or STA-BIL Storage for large volumes.
• Storing indefinitely. Even stabilized fuel has a window. Rotate it into running equipment within the planned storage period.

FAQ

How long does stabilized gasoline actually last?

STA-BIL claims up to 24 months at the double dose in ideal conditions (cool, dark, sealed containers with E0 fuel). In practice, most stabilized E10 fuel is reliably usable for 12 months. Ethanol-free fuel with stabilizer can store reliably for 2+ years. Results vary significantly based on temperature and container quality.

Can I use too much stabilizer?

Overdosing by 50–100% is generally harmless, extra stabilizer doesn't damage engines. Extreme overdose (5–10× the recommended dose) can potentially gum up injectors. Stick to 1–2× the recommended dose for long-term storage.

Does stabilizer work for diesel fuel?

Most gasoline stabilizers are not rated for diesel. Diesel has different degradation mechanisms (microbial growth, water separation, wax crystallization in cold weather). Use a dedicated diesel fuel additive or biocide designed for diesel storage.

Should I use stabilizer in my car's gas tank?

Only if the car will sit unused for an extended period (30+ days). For regularly driven vehicles, fresh fuel turnover is sufficient, adding stabilizer to a regularly used tank provides no significant benefit and wastes product.

How much STA-BIL do I need for a 5-gallon gas can?

At STA-BIL Storage's rate of 1 oz per 2.5 gallons, a full 5-gallon can needs 2 oz (about 4 tablespoons or 60 mL). A 1-gallon can takes roughly 0.4 oz, and a 2-gallon can about 0.8 oz. Double those amounts (so 4 oz for a 5-gallon can) if the fuel will sit longer than 12 months. Add the stabilizer before or during filling, then run the engine a few minutes so treated fuel reaches the carburetor.

Sources & references

• Gold Eagle (STA-BIL) for the 1 oz per 2.5 gallon dose and up-to-24-month storage claim.
• PRI Products (PRI-G) and Sea Foam for their respective label dose rates.
• NFPA 30 (Flammable and Combustible Liquids Code) for the ~25-gallon residential storage limit in approved containers of 5 gallons or less; local fire codes are often stricter.