Best Fuel Additive For Generators

#1 · Best Overall

1. Quicksilver Quickstor

Best for: Long-term gasoline storage.

Why it ranks #1: Its listed uses explicitly include generators, and it stabilizes fuel for up to two years at a stated dose of 1 oz. per 5 gallons.

Stabilizing gasoline for up to two years makes Quicksilver Quickstor a practical option for generators put away between seasons. Its stated ratio—one ounce treats five gallons—also gives owners a concrete way to scale treatment to a generator’s fuel supply.

Quickstor is specified for long-term storage of generators and other powered equipment, and it helps prevent regular and ethanol-blended gasoline from breaking down and oxidizing. The up-to-two-year stabilization period suits extended downtime, while the one-ounce-per-five-gallons ratio supports measuring treatment against the fuel volume being stored. It is produced to meet Mercury Marine original equipment specifications, but the supplied details do not identify it as a cleaner for an engine already experiencing rough running.

Skip it if you need a stated rough-running-engine cleaner; STA-BIL Fast Fix Small Engine Treatment targets hard starts, sputtering, and deposits.

Choose Quickstor when storing a gasoline generator and you want a defined treatment ratio plus protection for up to two years. Its listed strength is preserving fuel, not treating a generator that already runs poorly.

Listed on Amazon as: Quicksilver Quickstor Fuel Treatment and Stabilizer

#2 · Best Storage Pick

2. STA-BIL Storage Stabilizer

• Weight: 9.9 oz

Best for: Seasonal generator storage.

Why it ranks #2: Keeps fuel fresh for up to 24 months, works with ethanol and non-ethanol gasoline, and is listed for outdoor power equipment storage.

Fuel freshness for up to 24 months gives STA-BIL Storage Fuel Stabilizer a clear role in generator upkeep: preparing gasoline-powered equipment for downtime. It also works with ethanol and non-ethanol gasoline, supporting owners who want to leave fuel in stored equipment rather than drain the tank.

The stated 24-month fuel-preservation period helps make this a fit for generators that sit between seasonal uses. Its listed features also prevent gum and varnish buildup and help protect fuel-system components from fuel breakdown, addressing storage concerns beyond freshness alone. Because it works with gasoline including ethanol blends and eliminates the need to drain fuel before storage, it can simplify the seasonal put-away routine; the supplied facts do not describe repair treatment for an already rough-running engine.

Skip it if you need a treatment for existing rough running or hard starts; STA-BIL Fast Fix Small Engine Treatment specifically targets those symptoms.

Pick this for a gasoline generator that will sit through a season or longer and needs treated fuel left in its system. Its value is storage preparation; look elsewhere if your priority is addressing present running problems.

Listed on Amazon as: STA-BIL Storage Fuel Stabilizer, 10 oz

#3 · Longest Stated Storage

3. Ethanol Shield Stabilizer

• Weight: 8 lb

Best for: Bulk treatment for mixed engines.

Why it ranks #3: Claims fuel stabilization for up to three years and compatibility with all 2- and 4-cycle engines, making it suitable for varied generator types.

A one-gallon container that treats up to 1,280 gallons gives Ethanol Shield a bulk-use profile for owners maintaining several engines. The stabilizer is listed for both two- and four-cycle engines, so its stated compatibility spans common small-engine equipment types.

Ethanol Shield claims fuel stabilization for up to three years, providing a defined storage horizon for equipment that may sit unused. Its compatibility with all two- and four-cycle engines also makes the gallon container relevant to mixed fleets of gasoline-powered equipment, including generators. The listing says it prevents water issues and conditions rubber and plastic, connecting fuel protection with material care. Its large treatment capacity suits repeated use, though the supplied facts do not state a specific per-gallon dose.

Skip it if you want a clearly stated ounce-to-gallon ratio for storage; Quicksilver Quickstor specifies one ounce for five gallons.

This fits owners treating multiple generators or other two- and four-cycle equipment who can use a gallon of additive over time. Its long stated stabilization period is useful, but the supplied facts omit a per-gallon dose.

Listed on Amazon as: Ethanol Shield Fuel Stabilizer 1 Gallon (128 oz) Prevents Corrosion – Gasoline Treatment that Protects Fuel System- Fuel Saver – Treats up to 1280 Gallons.

#4 · Best Enzyme Treatment

4. Star Tron Gas Concentrate

• Weight: 1.02 lb

Best for: Fuel-system cleaning routine.

Why it ranks #4: The gasoline concentrate is described as cleaning the fuel delivery system and helping with ethanol-related problems, useful beyond basic storage treatment.

A concentrated enzyme blend that cleans the fuel delivery system is the central claim for Star Tron Gasoline Treatment. Its description includes fuel tanks and carburetors, while also stating that it improves combustibility in ethanol blends, linking system cleaning with day-to-day generator operation.

The listing says the treatment keeps working through the fuel delivery system, including the tank and carburetor, which gives generator owners a whole-system cleaning focus rather than a carburetor-only claim. Its proprietary enzyme blend is also described as improving combustibility across fuels including ethanol blends, with better power and fuel economy stated as outcomes. These claims make it relevant to routine gasoline-generator care, but the supplied information does not specify a dosage, capacity, or storage duration.

Skip it if you need a specified long-term storage interval and treatment ratio; Quicksilver Quickstor lists both for gasoline equipment.

This suits gasoline-generator owners seeking an enzyme treatment for ongoing fuel-system cleaning, including the tank and carburetor. Check that its unspecified dosage and storage duration fit your maintenance routine before choosing it for seasonal storage.

Listed on Amazon as: Star TRON Enzyme Fuel Treatment – Gasoline

#5 · Best for Rough Running

5. STA-BIL Fast Fix

• Weight: 7.36 oz

Best for: Rough-running small engines.

Why it ranks #5: Targets small-engine hard starts, sputtering, and rough running while cleaning carburetors and fuel components without disassembly.

Carburetor and fuel-system cleaning without disassembly is the key draw of STA-BIL Fast Fix. Its liquid treatment targets gum and varnish linked to hard starts, sputtering, and rough running, making it relevant for generator owners trying to address fuel-related trouble through the engine’s existing fuel system.

Fast Fix works through the fuel system to clean carburetors, injectors, and internal components, so the listed cleaning action does not require taking the carburetor apart. It also helps eliminate water and combat ethanol fuel effects, addressing more than deposits alone. Those features suit a small generator that starts poorly or runs unevenly after fuel issues; this is a treatment aimed at restoring operation, rather than a stated long-term storage stabilizer.

Skip it if you need a stated long-term storage interval; STA-BIL Storage Fuel Stabilizer specifies fuel freshness for up to 24 months.

Choose it when a small gasoline generator has hard-starting, sputtering, or rough-running symptoms and you want fuel-system cleaning without disassembly. Its supplied claims focus on cleanup and water treatment, not a defined seasonal storage interval.

Listed on Amazon as: STA-BIL Fast Fix Small Engine Treatment, 8 oz

#6

6. STA-BIL Small Engine Pro

• Weight: 1.1 lb

Best for: Gas-and-oil small-engine care.

Why it ranks #6: This small-engine gasoline and oil additive cleans gum and varnish, protects against ethanol, and lubricates internal components.

STA-BIL Small Engine Pro can be added to gas or oil, giving its cleaning and lubrication claims two routes into small-engine maintenance. It targets gum and varnish while also lubricating valves and pistons, a combination aimed at generator owners seeking broader care than fuel treatment alone.

When added to gas, the formula is described as cleaning gum and varnish to help restore lost power and performance. When added to oil, it lubricates and frees sticky valves and pistons, extending its stated use beyond the fuel system. Corrosion inhibitors address ethanol-related effects, and the listing also says the lubrication and cleaning can quiet noisy engines. This multi-system approach suits small-engine upkeep, although the supplied facts do not give a fuel-storage duration or treatment ratio.

Skip it if you need a stated storage interval for treated gasoline; STA-BIL Storage Fuel Stabilizer lists freshness for up to 24 months.

Pick Small Engine Pro for small gasoline generators when you want cleaning plus lubrication through either gas or oil. Its multi-system claims suit upkeep, but the listing does not specify how long it preserves stored fuel.

Listed on Amazon as: STA-BIL Small Engine Pro Multi-System Additive – Protects Against Ethanol – Cleans Carb and Injectors – Improves Engine Efficiency – Lubricates Valves and Pistons, 16 fl. oz. (22305)

#7

7. Star Tron Enzyme Treatment

Best for: Idle engines and ethanol fuel.

Why it ranks #7: Its 16-fluid-ounce gasoline treatment uses enzyme technology and is described as helping with ethanol fuel problems and starting after idle periods.

Star Tron’s enzyme technology is presented as a way to address water and sludge in gasoline, including ethanol blends. The treatment is also described for engines that have sat idle for months or are used daily, making it a flexible option for generator owners dealing with variable use patterns.

The supplied description says the enzymes break excess water and sludge into sub-micron size so it can be burned during normal engine operation. That approach connects water treatment to ordinary running rather than a listed disassembly step. Star Tron also states that it helps engines start easily and run smoothly with ethanol-blended or ethanol-free gasoline, giving generator owners fuel flexibility. The listing identifies a 16-fluid-ounce capacity, but gives no storage-protection duration or dosing rate.

Skip it if you need a stated storage duration or a clear treatment ratio; Quicksilver Quickstor specifies up to two years and one ounce per five gallons.

Consider it for a gasoline generator that alternates between long idle periods and regular use, especially when ethanol fuel or water concerns matter. The supplied details do not establish a storage interval or a dosing schedule.

Listed on Amazon as: Star TRON Enzyme Fuel Treatment – Gas, Stabilizes Old Gasoline

#8

8. Mechanic in a Bottle

• Weight: 8 lb

Best for: Bulk fuel-system cleaning.

Why it ranks #8: The 128-ounce gas-and-diesel formula cleans deposits and encapsulates water, but its gallon format is less convenient for occasional generator treatment.

On-machine cleaning of carburetors, injectors, and internal engine components is the core appeal of Mechanic in a Bottle. Its gallon jug also supports repeated maintenance, while the listed gas-and-diesel formula broadens its fit beyond gasoline-only generator setups.

The formula is described as removing varnish, shellac, and carbon deposits without disassembly, which can make fuel-system maintenance less involved. It also encapsulates free water and returns it to suspension in fuel to be burned out, addressing a different source of trouble during normal operation. Claims about restoring lubrication and reconditioning rubber and plastic add component-care benefits. The gallon size is suited to recurring use, though the supplied details do not give a treatment ratio or storage duration.

Skip it if you need a defined long-term gasoline-storage period and dose; Quicksilver Quickstor lists up to two years and one ounce per five gallons.

Choose it for recurring fuel-system cleaning across gas- or diesel-powered equipment, particularly when avoiding disassembly matters. Its gallon size and cleaning claims suit maintenance use, but the listing leaves storage duration and dosing unspecified.

Listed on Amazon as: Mechanic in A Bottle Gas & Diesel Formula, Gallon Jug. Fuel System Cleaner & Stabilizer, Maintain Peak Performance.

#9

9. Lucas Oil Fuel Treatment

• Weight: 898 g

Best for: Gasoline and diesel engines.

Why it ranks #9: Treats gasoline and diesel and cleans fuel-system components, but the supplied details do not specify a generator use or a storage duration.

Compatibility with both gasoline and diesel gives Lucas Oil Fuel Treatment a broader engine remit than a gasoline-only additive. Its listed cleaning and lubrication of injectors, carburetors, and combustion chambers makes it relevant to owners maintaining generators alongside other engine types.

Lucas Oil says the treatment cleans and lubricates the fuel system, including injectors, carburetors, and combustion chambers, tying deposit care to lubrication in one product. It also lists neutralizing sulfur and other harmful contaminants, while improving fuel flow and reducing deposit buildup are connected with stated power and acceleration benefits. That combination may suit owners maintaining multiple fuel types, but the supplied information does not give a generator-specific storage duration or treatment ratio.

Skip it if you need a defined gasoline-storage period and dose; Quicksilver Quickstor specifies up to two years and one ounce per five gallons.

Consider Lucas Oil for owners who want one fuel treatment for gasoline and diesel engines and value its stated cleaning and lubrication claims. It is less specific for generator storage because no duration or dose is listed.

Listed on Amazon as: Lucas Oil 10003 Fuel Treatment – 1 Quart

#10

10. Hot Shot's Secret EDT

• Weight: 16 oz

Best for: Diesel generator upkeep.

Why it ranks #10: This is specifically a diesel treatment, so it is a poor match for the gasoline-fueled generators addressed by most products in this roundup.

A cetane increase of up to seven points is the concrete differentiator for Hot Shot’s Secret Everyday Diesel Treatment. The product is specifically presented as a diesel additive, making it relevant to diesel-generator owners seeking routine fuel treatment rather than a gasoline-generator formula.

The listing positions EDT as an everyday treatment for diesel engines and says it boosts cetane by up to seven points, linking regular use with stated fuel-economy and performance benefits. That makes it a possible fit for diesel-generator upkeep where routine dosing is the goal. The supplied facts identify a 16-ounce liquid bottle, but do not provide a generator-specific dose or fuel-storage period, so owners cannot use this listing alone to plan long-term storage treatment.

Skip it if you run a gasoline generator; STA-BIL Storage Fuel Stabilizer is listed for gasoline including ethanol blends and storage.

This is for owners maintaining diesel generators who want an everyday diesel treatment with a stated cetane claim. The supplied details do not establish a generator dose or long-term storage role, so those needs require separate guidance.

Listed on Amazon as: Hot Shot's Secret Everyday Diesel Treatment EDT, 16 oz