AMSOIL Gasoline Stabilizer
AMSOIL Gasoline Stabilizer (product code ASTCN) is a long-term fuel-preservation additive built for seasonal vehicles, powersports machines, marine engines, and small power equipment that sit idle between uses. The formula slows the oxidation reactions that turn untreated gasoline into varnish, gum, and corrosive byproducts inside tanks, fuel lines, carburetors, and injectors, keeping the engine ready to start when the equipment returns to service.
Long-term storage protection up to 12 months
Untreated gasoline can begin to degrade in as little as 30 days, leaving behind sticky varnish, gum, and oxidized byproducts that clog jets, glue carburetor floats in place, and starve the engine of clean fuel at startup. Dosed before storage, AMSOIL Gasoline Stabilizer keeps fuel viable for storage periods up to 12 months, covering a typical winter or summer layup for boats, snowmobiles, RVs, classic cars, lawn tractors, and other equipment used only part of the year.
The treatment also removes the need to drain the tank before storage. Draining a bare metal tank invites flash rust on exposed surfaces and dries out gaskets and seals, both of which create new failure points the next time the equipment is started.
Eight times longer fuel stability vs Sea Foam
In a triple-length gasoline oxidation stability test (ASTM D525) using a base fuel containing no oxidation-stability-improving additives, AMSOIL Gasoline Stabilizer held off oxidation for 4,320 minutes versus 536 minutes for Sea Foam Motor Treatment, an eight-fold improvement in measured fuel stability. Based on independent third-party testing of AMSOIL Gasoline Stabilizer obtained July 1, 2022 and Sea Foam Motor Treatment purchased June 30, 2022 in a triple-length ASTM D525 test using fuel containing no oxidation-stability-improving additives.
Corrosion protection for metal tanks and fuel-system parts
Stored gasoline absorbs atmospheric moisture and acidic byproducts that attack carbon-steel tanks, fuel lines, and pump internals. In a modified NACE TM0172 test using synthetic sea water per ASTM D665B, AMSOIL Gasoline Stabilizer delivered corrosion protection on metal coupons that Sea Foam Motor Treatment did not match, helping preserve fuel-system metallurgy through long layups, including coastal and high-humidity environments.
Effective in ethanol-blended pump fuel
Most retail gasoline in the United States contains up to 10 percent ethanol (E10), which absorbs water and accelerates fuel-system corrosion when the equipment sits unused. AMSOIL Gasoline Stabilizer is formulated to remain effective in fuel containing up to 10 percent ethanol, protecting both two-stroke and four-stroke engines that share modern pump-station fuel.
Carburetor and injector cleanliness
Most no-start complaints after long storage trace back to varnish and gum deposits on float needles, idle jets, main jets, and pintle injectors. AMSOIL Gasoline Stabilizer attacks the problem at the source by inhibiting the oxidation chemistry that forms those deposits, lowering the odds of carburetor teardowns, injector flushes, and tank drops at the start of the next season.
Treat rate and pre-storage dosing
One ounce of AMSOIL Gasoline Stabilizer treats 2.5 gallons of gasoline, which means a single 16 oz bottle treats 40 gallons of fuel. Add the appropriate dose to the tank, then run the engine for five to 10 minutes so the treated fuel circulates through the entire fuel system from the tank to the carburetor or injectors. Stop the engine and place the equipment in a dry, covered location for storage.
Recommended applications and service intervals
AMSOIL Gasoline Stabilizer is suited to any spark-ignition engine that runs on gasoline, including E10 blends, and faces a meaningful storage gap between uses. The product is not formulated for diesel fuel; distillate-fuel storage uses different additive chemistry.
- Seasonal layup of cars, trucks, motorcycles, snowmobiles, ATVs, UTVs, personal watercraft, and classic vehicles for periods up to 12 months.
- Marine outboard, stern-drive, and inboard gasoline engines stored on the trailer, in the slip, or on the lift between seasons.
- Lawn tractors, push mowers, chainsaws, snowblowers, portable generators, and handheld two-stroke and four-stroke power equipment placed in a shed or garage for the off-season.
- Farm and powered construction equipment that sits between jobs or between growing seasons, including units fueled from on-site bulk tanks.
For shorter ethanol-fuel maintenance cycles in actively used powersports and small engines, and for deeper fuel-system cleaning, the AMSOIL fuel-additive line also includes Quickshot and P.i.; a side-by-side overview lives on the Quickshot fuel additive guide. Outside the United States and Canada, fuel chemistry and ethanol blends vary, so confirm storage practice and dose for the local market before treating equipment.
Typical specifications
| Property | Value |
|---|
| Recommended treat rate | 1 oz per 2.5 gallons of fuel |
| Maximum ethanol content of treated fuel | 10 percent (E10) |
| Maximum recommended storage life of treated fuel | 12 months |
| Fuel oxidation stability, ASTM D525 triple-length | 4,320 minutes |
| Engine circulation after dosing | Five to 10 minutes |
| Fuel type | Gasoline only, not for diesel |
Order AMSOIL Gasoline Stabilizer
AMSOIL Gasoline Stabilizer ships in a 16 oz bottle (ASTCN-EA), a case of six 16 oz bottles (ASTCN-CA), and a 55 gallon drum (AST55-EA), and is backed by the AMSOIL Limited Liability Warranty. Match the additive to the right equipment using the AMSOIL vehicle lookup guide and compare storage versus ethanol-management additives on the Quickshot fuel additive guide, then place the order through AMSOIL Gasoline Stabilizer.
Customer reviews
Amsoil products
I only use Amsoil products
By David from Orlando, FL on July 09, 2026.
Would recommend this to a friend.
Great for vehicle seasonal storage
I add this to the fuel in our Motorhome that sits parked about half of each year, with a full 55 gal tank. The end result is no issues whatsoever when we take it on trips! The AMSOIL Stabilizer keeps the fuel protected and road ready!
By Dustin from New Mexico on May 12, 2026.
Would recommend this to a friend.
Fuel Care
Works great UTV's Ben setting over a year and started right and ran great, Stabilizer worked really good
By Dan from American Canyon on March 18, 2026.
Would recommend this to a friend.
Read all 171 reviews
Frequently asked questions
How long does AMSOIL Gasoline Stabilizer keep gasoline fresh?
Treated at the recommended dose before storage, AMSOIL Gasoline Stabilizer keeps gasoline viable for storage periods up to 12 months. Untreated pump gasoline, by contrast, can begin to degrade in as little as 30 days, which is why long-term layup of seasonal equipment without a stabilizer often ends in carburetor varnish and hard starts the next spring.
How much AMSOIL Gasoline Stabilizer should be added per gallon of gas?
One ounce of AMSOIL Gasoline Stabilizer treats 2.5 gallons of fuel, so a 16 oz bottle treats 40 gallons. Add the dose to the tank, then run the engine for five to 10 minutes to circulate treated fuel through carburetors, injectors, and fuel lines before parking the equipment.
Does AMSOIL Gasoline Stabilizer work in ethanol-blended fuel?
The formula is designed to remain effective in fuel containing up to 10 percent ethanol, the standard E10 blend at most United States retail pumps. That covers the majority of pump gasoline used in cars, motorcycles, snowmobiles, lawn equipment, and other powersports.
How is AMSOIL Gasoline Stabilizer different from AMSOIL Quickshot?
AMSOIL Gasoline Stabilizer is built for long-term storage of gasoline-fueled equipment, with the goal of holding the fuel viable through a layup of up to 12 months. AMSOIL Quickshot targets shorter ethanol-related fuel issues in actively used powersports and small engines. The full side-by-side comparison is on the Quickshot fuel additive guide linked above.
Can AMSOIL Gasoline Stabilizer be used in two-stroke engines?
The product is intended for any gasoline-fueled engine that sits idle between uses, including both two-stroke and four-stroke equipment such as snowmobiles, motorcycles, chainsaws, weed trimmers, leaf blowers, and outboard motors.
Does using AMSOIL Gasoline Stabilizer void an OEM warranty?
Using AMSOIL Gasoline Stabilizer at the recommended dose in gasoline-fueled equipment does not void the original equipment manufacturer warranty by itself, and the additive itself is backed by the AMSOIL Limited Liability Warranty.
