Lawn MowersBlogBuying Guide

Fuel Additives For Lawn Mowers

New 2022 edition! We’ve made a few changes to our recommendations, to give you the best possible experience and get your lawn mower running again.

Whether you’re taking care of a small yard or an entire neighborhood, making sure your equipment works like it’s intended is vital. These gas additives will help keep your lawn mowers engine clean, free of gum and gasoline varnish, as well as protect against ethanol corrosion and poor-quality gasoline. Here’s our favorites for lawn mowers, and our expert opinion on which ones are best.

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IN A HURRY? No time to read, and want to know what works RIGHT NOW? Try Gumout Multi-System Tune-up, STA-BIL Fast Fix, or Seafoam.

What are fuel additives?

Fuel additives are chemicals that are designed to blend and mix with fuel, improving the properties of the fuel. Without getting too technical, here is a broad overview of common types of fuel additives:

  • Solvents, designed to clean carburetor jets, fuel pumps, and injectors of deposits and sticky residues.
  • Detergents, to help reduce carbon and fouling on valves and in combustion chambers.
  • Combustion Enhancers, which allow fuel to vaporize more easily and thus burn more thoroughly.
  • Antioxidants, which help to keep the fuel fresh for long periods of time, and help prevent corrosion.
  • Upper Cylinder Lubricants, which help fight piston ring and cylinder wear.
  • Decarbonizing agents, specifically to dissolve tough carbon deposits on valves and cylinders.
  • Water removers, to help water dissolve in gas better, so it does not build up in the tank.

Some additives like Polyetheramime (PEA) perform several of those jobs at the same time. The manufacturers of fuel additives extensively test to make sure that their blend is compatible with the types of fuel normally encountered.

Doesn’t gas already contain additives?

The federal government mandates a minimum of detergent additives in gas, to help reduce pollution and optimize efficiency. These detergents cost money however, and more detergent would mean more expensive fuel. At today’s already expensive fuel prices, this is a benefit that few would spend extra for. Some types of premium fuel brands market themselves as having much more detergent than the federal standards, but these detergents do little to help stabilize fuel for long term storage or remove water that has entered a fuel system. Combine that with ethanol fuels poor storage attributes as well as tendency to pull water from the air, and your basic gas from the pump just isn’t enough anymore.

Edit: As of 2022, a lasting supply crunch and our new world dynamic means that even the best fuel brands may not be putting in the amount of additives they once were. Fuel quality is down across the board- everyone is making ends meet, even big companies! Find an off the shelf product and add it to your fuel, seriously.


Ethanol in fuel is a mixed blessing. It’s much safer than the MTBE, which was used in the past, but tends to absorb moisture from the air. This moisture can cause rust, oxidization, and in some cases bacterial growth in fuel tanks. Ethanol based fuels are known to go stale much faster than the non-ethanol blends in the past. Without an additional stabilizer, some Ethanol blends have been known to go bad in as little as three months. This doesn’t matter for a daily driven car, but for a rarely used small engine, can be a disaster.

The best gas for lawn mowers is ethanol free, but in some locations you cant buy it, or it’s simply too expensive.

Fuel Additives for Lawn Mowers

Many fuel additives are multi-purpose, and useful in any engine- be it a snow blower, lawn mower, pressure washer, or other device. But the summer weather many people associate with mowing lawns means different needs than that of the cold winter months. In order of importance, we gauged additives effectiveness in this order.

  • Stabilize Fuel
  • Reduce And/or Prevent Ethanol Damage or Corrosion
  • Reduce and/or remove Carbon and Fuel System Varnish
  • Upper Cylinder Lubrication or Combustion Enhancement to Improve Efficiency
  • Water Removal

In the hot summer months, stabilizing fuel and preventing ethanol issues is going to give the greatest increase in reliability, followed by cleaning ability and improving fuel efficiency. Water removal is at the very bottom, as fresh gas tends to be readily available. If you’re having water issues, checking your fuel supplies as well as using a separator funnel can often solve many of these problems. So if you’re ready to have less rough starting, rough idling, poorly running equipment and are ready to explore solutions, read on and check out our recommendations below.

STA-BIL Fast Fix Small Engine Treatment

STA-BIL Fast Fix is a new option on the market- specifically designed for small engine use. It cleans carburetors and injectors, fixes rough running engines, and eliminates water from fuel – all major headaches for small engine owners. It’s designed to be a “one and done” to get you going again if you’re having fuel issues. The formula is made for both 2-cycle and 4-cycle engines, and can be used in lawn mowers, chain saws, pressure washers, generators, and other similar small engines. Fast Fix also claims to be able to remove carbon deposits, giving added value. The one thing we don’t like, the product is not a long term fuel stabilizer- we think this is a great option to get you going again, but you’re better off with their “360 protection” product if you want something that will also keep fuel fresh.

Chevron Techron Concentrate Plus

Chevron Techron is a best-selling product, primarily targeting the automotive market. It’s one of the earliest fuel system cleaners to contain PEA, a newer type of fuel detergent that works better in modern engines. Techron doesn’t claim to be able to stabilize fuel, however for rough running engines which are simply in need of a good cleaning; this could be a great choice. At a treatment rate of only 1oz per gallon of fuel, you get enough for 32 gallons of gasoline.

Sea Foam Motor Treatment

Is your mower a SeaFoam lawn mower? SeaFoam has quickly become the gold standard of fuel additives, originally made to help marine outboards run better. It’s popular among not just automotive circles but in small engine users as well; because it works. SeaFoam claims to be able to clean carb jets, reduce moisture in fuel, stabilize fuel up to 2 years, remove deposits, and lubricate your fuel system. Many users we’ve spoken to will use nothing else, because Seafoam does everything well enough. Or as the old timers would say- “Rough Idle? Just Add Sea Foam”.

Fuel Ox

Fuel Ox is a very cool newer product that contains a combustion catalyst, much like Archoil. They claim it will reduce the flash point of fuel, which means an increase of power and efficiency by up to 10 percent, and a 60 percent reduction in emissions. Fuel Ox is completely compatible with all common fuels including gasoline and diesel. In addition to improved performance, fuel ox removes water from gas, protects against ethanol corrosion, lubricates upper cylinders, and stabilizes fuel. This makes Fuel Ox a solid contender on our list

We really like the fact that Fuel Ox reduces emissions- while we like keeping our equipment running right, making sure fuel burns better means more gas spent on work and less blown into the sky. Good for your wallet, good for the environment, everyone wins.

Marvel Mystery Oil

Marvel Mystery Oil has been around since 1928, and its red colored bottles and wintergreen scent have graced many a garage. While not containing advanced technology like some of the other additives we’ve mentioned, it’s still a great basic fuel additive for carburetor engines. The formula can also be used in oil to help clean and remove sludge. Cost is generally low and at a treatment rate of only 2 oz for every 5 gallons of fuel, it tends to be economical to use constantly as well.

Many of our experts anecdotally have noticed less fuel use as well as an elimination of spark plug and carbon fouling with using Marvel. It’s not going to be able to remove water from your fuel tank but is still a solid all-rounder for general use. The old timers also like to use this as a household oil and in their air tools, something we’ve started doing as well.

GumOut Multi System Tune-Up

GumOut sells an entire line of fuel additives and fuel system cleaners, but their Multi-System Tune-Up product has become a favorite. Multi-System Tune-Up contains PEA, a newer technology type of detergent that is specifically optimized to clean better than traditional solvents alone. Otherwise it’s like SeaFoam in versatility. GumOut stabilizes fuel, cleans the fuel system, reduces harmful deposits, and fights fuel system corrosion.

STA-BIL Original

Sta-Bil has been around for a long time, and for many this was the first fuel additive they ever heard of. Primarily a fuel stabilizer, it also helps to remove water, prevent corrosion, and keep your fuel system clean. Stabil claims to be able to stabilize fuel for up to 2 years. We’ve found that while this is a good product, it doesn’t seem to be as effective in ethanol fuels. Use it if you have it, but we’d recommend using the 360 products over this one if you can find it.

STA-BIL 360 Protection

Sta-Bil 360 is like original Sta-Bil, mainly being a fuel stabilizer. However, unlike the original, this product is specifically designed to give protection against ethanol- at the cost of only stabilizing fuel for 12 months instead of 2 years. Sta-Bil 360 also helps reduce harmful gums and fuel system varnish, to keep the carburetor or injectors of your equipment clean. If you wanted fuel stabilizer for lawn mower and other small equipment, but also want extra cleaning and protection- 360 protection is a great all-round choice.

PRI-G Complete Gasoline Treatment

The G in PRI-G stands for for “Gasoline”. Described by some as “Stabil on Steroids”, PRI Research claims that PRI-G can restore even stale, bad fuel to a usable condition. This means PRI-G could be the best fuel treatment for bad gas. PRI-G vs Stabil has become the new “which truck is better?” among some we know, and we know better than to get into that fight. PRI-G makes the usual claims like other additives, about improving combustion efficiency and fuel system cleaning. What we do know- regular users of PRI-G absolutely swear by the product, with reviews online saying the same. If you need a fuel additive for old gas, this is the one!

Archoil AR6200

ArchOil is a newer product, and very popular among users of Diesel Engines. However, Archoil AR6200 can also be used in gas. This product is primarily a combustion enhancer, claiming up to a 5% improvement in overall MPG. In fuel injected machines this may very well reduce the fuel required, but we’ve found that in traditional carburetor equipment it seems to have little effect. Archoil AR 6200 also contains a fuel stabilizer, and some amount of detergent to help remove fuel system varnish and keep the engine clean.

Updated for 2022: This product has become hard to find. If you liked this product, Fuel Ox, also reviewed on this page, is similar in many aspects to the Archoil Fuel Treatment.

STP Ultra 5-in-1 Plus System Cleaner and Fuel Stabilizer

STP Ultra 5-in-1 Plus seems to be the best “general purpose” additive we’ve tried. STP claims that 5-in-1 plus contains 3 times the amount of detergent as normal gasoline, plus contains a strong dose of fuel stabilizer and ethanol fighting power. We’ve tried this in not just our lawn mowers, but snow blowers and cars as well; and it works equally well in every application. Like the Gumout and Seafoam products, STP Ultra 5-in-1 Plus is a multipurpose additive, that can be used in the oil as well as fuel. This is our current favorite of the bunch, and we think you’ll like it too.

Star Tron Fuel Treatment

Star Tron Fuel treatment uses an enzymatic technology to prevent ethanol related gas oxidization, as well as stabilize fuel and help keep engines clean. The manufacturer makes strong claims about rejuvenating old gasoline and “curing ethanol problems”, specifically regarding small engines. The treatment rate is EXTREMELY economical, with a 16oz bottle being able to stabilize 256 gallons of gas. We’re not sure about those claims, but for the value minded consumer this could be the one to get. Star Tron also helps to keep engines clean and help reduce and/or eliminate gum and varnish in the fuel system. This gets our value pick due to the very economical treatment rate. A little seems to go a long way with this stuff, and the high reviews seem to back that up.

Lucas Ethanol Fuel Conditioner With Stabilizers

A new take on an older product, Lucas Fuel Treatment has been around a long time, and is popular in the Truck and Racing communities. Lucas Ethanol Fuel Conditioner was specifically developed to help address and resolve fuel issues due to ethanol use – namely fuel system corrosion. The product is compatible with any grade of gasoline , including E-10, E-15 and E-85. In addition to preventing corrosion, Lucas contains inhibitors to help stabilize fuel over time, and additives to help clean injectors, valve seats, combustion chambers, and other critical parts. If you like the Lucas brand products and know them well, we think this one will also be a solid performer.