Bad Fuel Symptoms. Lawn mower gas stabilizer

16th June 2023

Bad Fuel Symptoms

You make your way to the garage or shed, ready to tackle the day’s yard work, only to find that your lawn mower won’t start.

Did you know that bad gas is one of the most frequent causes of small engines not starting? Read on to learn about how to diagnose and treat engines affected with bad gas.

How long can gas be stored before it goes bad?

Whether in a gas can or in your mower, gas can go stale and lose its volatility in as little as 30 days. Using Sta-Bil Storage Fuel Stabilizer can increase storage time up to 24 months. Of course, many factors contribute to how long gas can be stored, including storage location, temperature, condition of the fuel container, and more.

How to Winterize your Lawn Mower with Fuel Stabilizer

What are the symptoms of bad gas?

If your lawn mower is difficult to start, idles roughly, stalls out, or makes a “pinging” sound, you may have a case of “bad gas”. And no, we’re not talking about the after-effects of dinner at your favorite Mexican restaurant.

How can I tell if the gas has gone bad?

The easiest way to diagnose gas is to smell the fuel in question. Oxidized gas has a sour smell and is much stronger smelling than fresh gas. The other method is to drain a sample from your machine’s fuel tank or your gas can into a clear glass container. If the gas is dark in color, it has more than likely gone bad. See the image below for a comparison between the color of fresh gas (Left) to gas that has oxidized (Right) and should not be used in your equipment.

Note the color of fresh gas (Left) compared to gas that has oxidized (Right)

What should I do if my equipment has bad fuel?

The best solution is to drain the gas from your equipment and replace with fresh gas. Remember to properly dispose of the old fuel.

How can bad gas affect my lawn mower?

If fuel was stored in the unit for an extended period, areas such as fuel lines and the metering needle may have become gummed up from the old fuel mixture. As gas ages, hydrocarbons in the fuel mixture evaporate and the remaining fuel becomes tacky or varnish-like. This can cause deposits and blockages in your equipment’s fuel system. In severe cases, professional cleaning of the carburetor and a possible carburetor rebuild are the only cure for this situation.

To verify this condition, remove the spark plug(s). If you can’t smell fuel in the combustion cylinder or see or smell fuel on the bottom of the spark plug, the fuel passageways are likely obstructed. If the carburetor is clogged, the use of spray carburetor cleaner and pressurized air may clear the obstruction. If this fails, then you should contact an experienced engine service center to have the system professionally and thoroughly cleaned.

Get the Parts and Tools You Need to Maintain Your Equipment Here at MTD Parts!

Spark plug wrench or socket tool (common sizes are 5/8″, 3/4″ and 13/16″)

Forgot to Winterize Lawn Mower: Effects and How To Fix It

If you forgot to winterize lawn mower and now it won’t work properly, there are some remedies you can try to save your mower. Who hasn’t been lazy for a year or two when we just put our lawnmowers away without emptying their fuel tanks and cleaning them properly first?

In this complete guide, our team has compiled all the possible negative consequences that could occur because of this unfortunate oversight.

You will also discover what you need to do to bring your mower back to life again.

What Happens if You Forgot to Winterize Your Lawn Mower?

If you forgot to winterize your lawn mower before being stored for the winter, it will fail to work properly in the upcoming spring season. What happens is that the fuel in the gas tank goes bad and causes corrosion and blockage of engine parts.

Other effects of not winterizing your lawn mower include the spark plug becoming damaged. debris building up in the carburetor and causing a blockage, the battery wearing out, and heavy corrosion occurring in the mower. Here are some more effects that are caused by not winterizing lawn mowers.

– The Gas Goes Bad

Removing gas from the fuel tank is an important part of winterizing a lawn mower. Otherwise, the gas goes bad over the winter months and ends up being harmful instead. This is especially true if a fuel stabilizer is not added to the gas to make it last through the winter.

The gas goes stale and breaks down into harmful components. Not only is stale gas no longer able to fuel the engines working, but its breakdown products will cause blockage and harm to different parts of the mower engine. Most gasses break down into a gum-like sticky residue that blocks the engine parts and is difficult to clean.

– The Spark Plug Might Die

A spark plug is one of the central components of your lawn mower’s engine machinery. Unfortunately, certain older designs of spark plugs can be susceptible to cold and get damaged if not winterized properly. over, if you have left the mower at the mercy of cold winds, rain, and snow, the spark plug will be the first to get corroded.

It is quite straightforward to see when the problem lies with your spark plug. Either the engine will not start to begin with, or it will start but the mower will fail to turn. Read your mower’s instructions manual to see where the spark plug is located and then inspect it.

In most mowers, the spark plug is located either on the back of the machine or its sides. It is a slight protrusion from the mower’s body, and you will have to unscrew its protective cover to gain access to it. In some cases, the spark plug needs a good cleaning, but in the worst-case scenario, you will have to replace it altogether.

– Debris Will Build Up in the Carburetor

As a consequence of not properly emptying the fuel tank before storing the mower for the winter, you will have to deal with a clogged carburetor later. The fuel breaks down. and its constituent products end up as grease and other glue-like substances that block the engine’s carburetor and other tiny passageways.

The carburetor is located within the engine. just behind the air filter. Most modern lawnmowers’ air filter is towards the machine’s side. It is covered by a meshwork protective covering that needs to be unscrewed. After removing the air filter, you can access the carburetor and see how completely covered in black junk it is.

– The Battery Wears Out

Most of us do not use our lawnmowers from the end of autumn through winter until the beginning of spring. The battery is at risk during all these long and cold months of no use. First, forgetting to take it out might cause the battery to be fully exposed to the cold winter.

The battery fluids freeze over and expand, damaging delicate parts in the process. Secondly, if the battery is not stored properly and is exposed to moist air or snow, this would cause its various parts to corrode and stop working.

Even when the battery was taken out before winter and stored properly, it would still lose its charge. and you will have to recharge it all day before it can be used again.

– Corrosion Might Occur

Your mower is at risk of getting its parts corroded from gaseous breakdown over the winter. Corrosion is more severe when poor-quality gas containing ethanol is used. Over time, ethanol absorbs moisture from the air and then corrodes the fuel tank, the carburetor, the pipes of the machinery, etc.

Corrosion is unhealthy for the machine because while some parts can be cleaned and replaced easily, others are much trickier. Hazardous gas and oil used as lawn mower fuel is something we would never recommend.

How Do You Fix a Mower That Has Not Been Winterized?

To fix a mower that has not been winterized and is now faulty, it is important to clean its fuel tank and add fuel to it that is clean and stabilized. It is also important to clean residue from other components, such as the air filter and the carburetor.

The spark plug should also be fixed if it has become faulty, and the lawn mower vent should be cleaned. It would be wise to add a fuel stabilizer to the fuel for future winter seasons.

– Clean the Air Filter First

The carburetor is usually accessible from the outside via an air filter. This filter and the carburetor must be cleaned first so the mower can start working properly again.

Technically, the air filter must be cleaned after a mowing usage of roughly 25 hours, but since yours has been lying in dust all winter, it needs to be cleaned before the mower is used again.

Before you can even go near the air filter, you must ensure that the mower engine has been turned off and that the key is out.
Loosen the screws holding the filter’s protective covering in place. Once the outer covering has been removed, carefully take the air filter out.
Your air filter will be made of either foam or paper, so you must check if it can be salvaged. Hold the paper filter upto a lightbulb and discard it if it seems to block most of the light. If not, then go ahead and tap it on a table to get the dust off.
On the other hand, you must discard the foam type of air filter when it becomes completely black and deformed. Otherwise, soak it in a water and soap solution for 15 minutes to remove all the accumulated dirt.

Only reinstall the filter back when it becomes 100 percent dry. While you have the air filter opened up, you should take the carburetor out and clean it as well.

– Clean the Carburetor Next

To clean the carburetor, you must detach all of the links connecting it to the engine. Put on your thickest pair of rubber gloves and disconnect the cables that connect the carburetor to the throttle and choke. Use a screwdriver to loosen the few bolts that hold the carburetor attached to the engine.

Disconnect the fuel line and keep a bottle ready to collect the fuel that will eventually drip. Finally, before disassembling the whole assembly, it is safe to take a picture. This way, you can always refer to how everything is supposed to look once you start reassembling everything.

Some carburetor parts, like a gasket, need to be replaced more often than others. If there is significant damage on any other parts, then those need to be replaced by newer ones. As for the rest of the carburetor parts, clean all of them using a toothbrush and a soap solution. Let everything air dry throughout its time. and then reassemble it.

You can also purchase a special carburetor cleaning commercial solution if you like. Have all the tiny parts soak in this solution for about an hour before you wash them with clean water. With a professional cleaning solution, there is little risk of corrosion occurring on the metal parts.

– Fix the Faulty Spark Plug

The spark plug is one delicate part of your lawn mower’s machinery. It is not surprising to see it not working after you fail to winterize the mower for a long period of time. Either the engine will fail to start from the get-go or will die soon after starting.

The front of the mower is the most probable location where a spark plug might be located. Before you touch it, double-check that the engine has been turned off. You want to avoid electrocuting yourself accidentally while fixing the spark plug.
A wrench can disconnect the spark plug from the mower body. It will most likely be coated in greasy residue from fuel breakdown. Sometimes, the spark plug even appears corroded after a long time of unuse.
You cannot soak the spark plug in soapy water for any time whatsoever. Just spray a little brake grease cleaner on the greasy parts and let it stay there for 20 to 25 minutes before wiping it off using a clean cloth.
Once the plug dries completely, put it back in its place and secure the bolts carefully using a wrench.

– Clean the Lawn Mower Vent

Sometimes, we take the mower out after months of not winterizing it and it seems to start just fine. However, it then sputters and comes to a halt soon afterward. In this particular scenario, the most probable cause is a fuel vent that has become defective.

The vent within the fuel cap of the engine is responsible for the flow of fresh gas from the fuel tank to the carburetor. The gas builds up within the tank when the vent becomes clogged by fuel breakdown products. Consequently, the engine starts alright but stops as the fuel flow is disrupted.

Most of the time, just detaching the fuel cap and reattaching it fixes the vent. Otherwise, you might have to clean the residue off it by soaking it in soapy water for 15 to 20 minutes. If the problem persists even after this, you will have to replace the old lawn mower vent with a new one.

– Clean the Fuel Tank and Refill It

One of the biggest disservices we commit by not winterizing our lawnmowers is towards the fuel tank.

This is where most of the gas breaks down into toxic and congealing by-products. This tank needs to be rid of the old fuel and cleaned from all the dirt and debris before you can refill it with fresh gas.

Take all the safety precautions by wearing gloves and goggles, turning the mower engine off, and disconnecting the spark plug. As always, never smoke while working with gasses or oils nearby.
If you have a siphon drain, drain the old fuel from the tank. Otherwise, disconnect the gas line that attaches the carburetor to the tank and place a container underneath. Collect the spilling fuel from the gas line into this container and store it for the time being.
You cannot use any water-based cleaning solution to clean the insides of a fuel tank. It would help if you bought a special oil-based cleaning solution for this procedure. Pour it onto the tank. close it off and shake the mower so it reaches every nook and corner.
After 5 to 10 minutes, drain the cleaning solution and refill the fuel tank with brand-new fuel.

– Add a Fuel Stabilizer to the Fuel

It’s okay to avoid winterizing lawnmowers by emptying their fuel tanks. Make sure you are using the best possible quality of gas and oil available in the market.

Lawn mower fuel needs to be high-octane, ethanol-free, and have fuel stabilizer added to it. Such a fuel will last at least six months within the tank without going bad and will also tolerate colder-than-average temperatures.

Conclusion

Let us summarize the important points discussed in this article about forgetting to winterize your lawn mower.

Winterizing a lawn mower means you empty its fuel tank, clean its parts such as mower blades, and keep it in a temperature-regulated place.
If mowers are not winterized for the season, the old gas and oil will go bad and deposit sticky residue everywhere.
The mower parts will need extensive cleanup before the machine can cut grass again.
Using premium-quality fuel with a fuel stabilizer containing zero percent ethanol will prevent many of these problems.

The next time you take your mower out of the tool shed after several months of being unused, do not be shocked when it refuses to start. Go through all the hacks discussed in this article and get your machine back on its feet immediately!

Is Too Much Fuel Stabilizer In A Mower Bad? (Answered)

This time-old saying clearly recommends the use of moderation (or the instructions on the back of the label). Can the same extend to the use of chemical agents in lawnmower maintenance?

Though adding too much fuel stabilizer in a mower is not bad per se, it is not recommended to exceed the levels the manufacturer recommends on the product packaging. Though excessive levels can cause clogged carburetors or engine corrosion over time, it is not likely.

That’s what we’ll be looking at today, as we discuss fuel stabilizers and the best way to use them. Some people might think, “more ‘stabilizer’, more ‘stability’”, but is that really the case? Are there any problematic consequences and, more importantly, solutions?

Can You Use Too Much Fuel Stabilizer In Your Mower?

The relatively infrequent use of private lawnmowers, coupled with the need to put them away during harsh winters, means machines that run on gas and diesel may retain fuel for very long time. This leads to the need for a stabilizer, but can this be overdone?

You can use too much fuel stabilizer in your lawn mower, but the results are normally not dire and in some cases not noticeable. It can clog carburetors and cause corrosion over extended periods of time, but over adding fuel stabilizer normally will just waste stabilizer.

This doesn’t mean that you should just pour in stabilizer into any amount of fuel without measuring. There are specific properties that it has and with the right mixture it can add months or even a year to the storage life of most gas and diesel fuels.

How to Diagnose Bad Fuel in a Riding Lawnmower

Why Should You Use Fuel Stabilizer?

The trouble with storing fuel in machinery or even containers for long periods is the series of chemical reactions and re-reactions that lead to the overall degradation of the fuel, as essential components escape through evaporation.

Fuel stabilizers in lawn mowers or in any gas tank for that matter, lengthen the time you can store gasoline or diesel before degrading makes the fuel unusable in combustion engines. It also stops sedimentation that creates particles capable of clogging carburetors.

In addition to degrading the fuel itself, the reactions can have a corrosive effect on the container (or fuel tank) the fuel is stored in. This may result in the chipping away of particles from the container, which adds to the already existing sedimentation in the fuel.

These particles can clog up near vital spots in your fuel system or engine, which is bad news.

While these reactions are much faster in gasoline, diesel fuel cannot be stored forever either.

So, ultimately, this reactivity and sedimentation means that combustion fuels are not stable…and that’s where fuel stabilizer comes in.

How Much Fuel Stabilizer Should You Use In Your Mower?

Fuel stabilizer is a chemical agent that drastically slows these reactions down while destroying particles that would otherwise be harmful to the mower’s fuel tank or fuel system. This makes the fuel much more storable over extended periods (several months to a few years, depending on the type).

A typical recommended mixture of fuel stabilizer is one ounce to two and a half gallons of fuel. Usually, the label on the stabilizer container has mixing instructions you can follow. You can mix the stabilizer in the gas tank on the machine itself or in a separate container.

I recommend that you carry out the mixture in a canister, or some other measuring container, so you can be sure of your fuel and stabilizer volumes before you add the mix.

Can You Use Too Much Fuel Stabilizer?

So, now we are back to our original question. If there are recommended amounts to use when mixing with gasoline and diesel, is it possible to use too much?

Exceeding the recommended mixture levels of fuel stabilizer to gasoline is generally not a good idea because the consequences may vary. However, in almost all cases, using too much stabilizer is simply a waste of good fuel stabilizer. It will not be harmful in the short term.

A little definitely goes a long way and it is not unheard of for a bottle of stabilizer to last years due to sparing use.

Some long term effects of too much stabilizer could include carburetor blockage and even corrosion, although these usually depend on the specific brand of stabilizer used as well as the quantity.

So, all in all, while adding too much stabilizer is not the end of the world, it’s best to stick to the specified mixing instructions, or to consult a professional.

What Happens If Too Much Fuel Stabilizer Is In Your Mower?

There are always mistakes, and I am definitely not the exception. I have added 2 cycle oil mixtures twice to the same gas can before realizing it and I am sure I have done the same thing with fuel stabilizers. So, what would be the result if you did this in your mower?

In most cases, nothing will happen if you put too much stabilizer in your lawnmower. Most brands of stabilizer won’t do anything besides reduce the rate of the fuel’s chemical reactions. Diluting gasoline or diesel with other elements will always take away from combustion levels, if only slightly.

However, in some cases, this can lead to the clogging of vital carburetor components, which can affect the combustion process and, ultimately, the performance of the mower.

The wrong mixture can even lead to corrosion of parts of the mower’s fuel and engine systems, particularly if you are using a de-varnishing stabilizer. This corrosion can even result in fuel leakages in some areas.

Fortunately, such effects are unlikely to occur if you miss the recommended mark by a few ounces.

What To Do If You Add Too Much Fuel Stabilizer In A Mower?

If you happen to go over the recommended volume of fuel stabilizer, do not panic, as there are solutions for various scenarios.

If 4 to 5 ounces over recommended levels of fuel stabilizer are added to a mower’s gas tank, no action needs to be taken. If 6 ounces or more are added over the limit, immediately run it until the tank is empty. The tank only needs to be manually emptied if an anti-varnish stabilizer was used.

If you missed the mark by a few ounces (e.g., 5 ounces instead of one), there’s not really any need to do anything unless you notice an effect on the mower’s performance. Just run the mower as you normally would and avoid repeating the mistake.

If you mixed the fuel with a lot of stabilizer, there is a risk that the carburetor may get clogged. You will have to run the mower as usual and carefully note how it performs.

In cases where an anti-varnish stabilizer has been used, the fuel tank should be emptied immediately to minimize any damage to the fuel system. The fuel lines, in particular, are especially thin, which makes them susceptible to leaks if they get thinned out any further.

How To Empty Anti-Varnish Fuel Stabilizer From A Mower Gas Tank

Emptying the mower fuel tank is a fairly simple process. Let’s look at the steps to take in case a large amount of anti-varnish fuel stabilizer somehow ends up in your mower.

You can either use a siphoning pump or a pair of hoses to empty nearly any mower gas tank.

Emptying A Mower Gas Tank With A Siphoning Pump

You start by placing the mower on a flat, and paved surface to avoid spilling any fuel on your lawn.
If you are using a siphoning pump, stick one end in the tank and the other in an empty fuel collection canister.
Start the siphoning pump to start the drainage and collect the fuel.
Once the pump is no longer able to siphon out any more fuel, you will have to add more fuel to dilute any remaining stabilizer.

Emptying A Lawn Mower Gas Tank Without A Siphoning Pump

Simply place one long hose into the tank, making sure that the end is submerged.
The other end of the long hose must go into your collection canister.
Next, place a shorter hose into the tank, but keep that end above the fuel level.
The other end should just stick out of the tank.
Then, using a damp cloth, seal the fuel tank opening and leave the two hoses as the only out/inlets.
Next, you must blow into the short hose to increase pressure in the tank, which forces the fuel-stabilizer mix to move up the long hose and into the canister.
Again, add more fuel once the siphoning is over.

What To Do With Fuel Mixed With Stabilizer After Removal

Once you’ve collected the fuel, you must inspect it to see if it is actually usable. If it is, you can dilute it with more fuel to remove the excess stabilizer.

Otherwise, you will have to dispose of the mix safely. Do not dump it, as the law frowns on that. Also, do not dump it on your lawn because this will kill the grass and even affect soil fertility.

The Final Touches On Using Too Much Fuel Stabilizer In Your Mower…

Is it bad to use too much fuel stabilizer in a lawn mower? Not really, no. As long as you don’t use more stabilizer than fuel and it isn’t an anti-varnish type of stabilizer, you should be fine. If you use a ton of extra in a mixture and it is already in the mower tank, you should just run the mower until the tank is empty without letting it sit.

The only real reason to manually empty a tank with a siphoning pump or the DIY tube method is if anti-varnish is present in the mixture.

Hopefully this help put your worries to rest.

Mathew has worked in landscaping professionally for over 10 years. He is a grandpa and frequently interviews other experienced landscapers and lawn care experts who are also grandpas for these articles.

About Us

We are Jerry McMillan and Mathew Booe (Father-In-Law/Great-Grandpa and Son-In-Law/Grandpa). Jerry has been in the landscaping business professionally for over 45 years and 10 of those years Mathew worked with him and helped him run his business. Together they answer landscaping, lawn care, and gardening questions of all types from hard work, first hand knowledge, and experience.

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The Best Fuel Stabilizer, According to 11,300 Customer Reviews

Welcome to the Thomas guide to the best fuel stabilizer 2023. Thomas has been connecting North American industrial buyers and suppliers for more than 120 years. When you purchase products through our independent recommendations, we may earn an affiliate commission.

Starting up cars, trucks, or other engines that haven’t been used in quite some time can lead to fears of corroded parts, deflated tires, and fuel that has gone bad. The most troublesome is often how the fuel has held up, but fortunately, there is a category of products that can bring fuel back from its gummy, gelled-over state of being.

Fuel stabilizers are hailed for their ability to preserve gas that’s been sitting for a long time. They’re all similar in how they work, but some are made specifically for different fuel types, engines, seasons, and detailed problems. Here’s a brief synopsis of how they work, what they affect, and some of the best fuel stabilizers on the market.

How Fuel Stabilizers Work

If collector cars, or any vehicles or tools, including power machines like blowers, mowers, boats, or generators, haven’t been used in a while, fuel can start to degrade and separate. Stored fuel, whether it’s kept in storage containers or left sitting in the fuel tanks themselves, can degrade and become contaminated with things like excess water over time.

When left too long, the entire fuel system can be damaged and parts can get clogged or jammed up. To prevent this from happening, it’s best to add a stabilizer to the fuel prior to letting the vehicle or machine sit. Any machine that is destined to go unused for three months or longer should have a stabilizer added to the tank with the fresh fuel.

Both systems that use ethanol fuel and diesel fuel can benefit from a fuel stabilizer, but it’s best to ensure the product being considered is compatible before buying or using. There are also specialized marine fuel stabilizer options that are best suited for marine engines. It should go without saying, but always read the label prior to buying.

Do Fuel Stabilizers Affect Fuel Economy?

There is a common misconception that fuel stabilizers can improve fuel economy (aka fuel efficiency). Fuel stabilizers can keep fuel in a useable state, but they don’t have the power to make gas or your vehicle’s fuel system more efficient—in fact, no fuel additive really can. Fuel economy is based on the vehicle’s makeup and construction. It may affect gas mileage in a roundabout way as it can clear up blocks and sludgy fuel.

For cars and trucks struggling with fuel economy or having overall gas mileage trouble, it’s best to see a technician, mechanic, or another professional who can diagnose the problem. Proper maintenance in tandem with a good stabilizer prevents ethanol fuel problems (and diesel) down the road.

Do Fuel Stabilizers Affect Fuel Injectors and Fuel Systems?

Fuel stabilizers can positively affect fuel injectors and other parts of the system in two ways mainly. Firstly, by preventing old gas from degrading, gelling, or gumming up, they indirectly relate to healthier, functioning parts and thus better engine performance.

Secondly, some stabilizers can help lubricate and clean the inner workings of an injector or fuel tank. Rarely do they negatively impact engines and fuel tanks, but be aware of the type of fuel stabilizer being used, how old the gas is, and how much is being poured in to avoid too much fuel stabilizer.

Here is a list of the best fuel stabilizers, followed by a buying guide to help you select the best fuel stabilizer for your needs.

Thomas’ Top Picks for the Best Fuel Stabilizer 2023

The following fuel treatment options are rated highly by customers and will help stale fuel from ruining machines, vehicles, and other powered items.

Best Fuel Treatment for Motorcycles: Lucas Oil 10303 Fuel Stabilizer | Buy Now

Best Engine Restart Formula: Start Your Engines! Fuel System Revitalizer | Buy Now

Best for Diesel Engines: STA-BIL Diesel Fuel Stabilizer | Buy Now

Scroll down to see our top picks for the best fuel stabilizer according to happy buyers.

listed in this article were as shown in US on amazon.com (USA) and other retailers as of November 2022

Best Overall Fuel Stabilizer—STA-BIL 360 Protection Ethanol Treatment Fuel Stabilizer

With this STA-BIL fuel stabilizer added to a gas tank, stored gas will stay good for up to a year and gasoline engines will therefore be protected from sludge and corrosion.

The formula itself can last for up to two years and is a viable additive for everything from cars to generators to lawnmowers. For best results, it’s important to add STA-BIL prior to filling up a tank at a gas station or a gas storage container so it mixes properly.

“I have used it before with great results so I bought more for this upcoming winter weather,” explained a customer. “Using on an HD Motorcycle and two Yamaha Waverunners for the third year straight, and have never had issues with bad fuel when it comes time to pull them out of storage.”

Fuel type: Ethanol and non-ethanol blends

Gallons of fuel treated: up to 160

Best Fuel Stabilizer for Cleaning and Stabilizing—Star Tron Enzyme Fuel Treatment Concentrate

Star Tron’s Enzyme fuel treatment is more than just a fuel stabilizer. It’s made to clean out a fuel system and keep the fuel tank, gasoline engines, and injectors in tip-top shape.

It functions by decomposing contaminants into tiny particles, which are then removed when the engine burns fuel again. Any stress over an accidental heavy pour can dissipate, too, as systems can’t be overloaded or overdose with this formula.

“It especially works great for all engines that may sit for quite some time between uses, it keeps the gas from separating and varnishing,” described a customer. “I use it extensively in my 2-cycle engines to keep the small hoses soft for years—I typically get 2–3 years out of my trimmer fuel lines now as compared to 8–12 months without.”

Gallons of fuel treated: 2,048

Best Outdoor Power Equipment Fuel Stabilizer—Yamaha Yamalube ACC-FSTAB-PL-32 Fuel Stabilizer Conditioner

Gasoline engines that tend to sit around most are those in power tools and generators. Many lay inactive for seasons unused until they’re needed again, and to keep fuel fresh, Yamaha made Yamalube, an alcohol-free formula that’s superb for small engine equipment.

This is suitable for two- and four-stroke engines, whether it’s being used in a leaf blower, chainsaw, or trimmer. A handful of reviewers found this stabilizes fuel in boats successfully as well as Waverunners (and other watercraft).

“I can attest that this stuff was in the fuel tank of an older riding lawnmower, that was stored outside, for five months during the winter,” wrote a buyer. “Rain, snow, freezing weather, and then some hot weather as spring came. The lawnmower started right up. Perfect. No long cranking, no chugging. I didn’t even top-off the battery first.”

Gallons of fuel treated: 96 gallons

Best Fuel Treatment for Motorcycles—Lucas Fuel Stabilizer

This Lucas fuel stabilizer is great for a variety of gasoline engines, but many reviewers rave about it when it’s used to store fuel for and in motorcycles. The alcohol-free formula performs well in both two- and four-cycle engines.

When mixed with fuel (fresh) it prevents it from degrading and won’t harm injectors or carburetors. Lucas also sells it in five and 55 gallon containers for businesses or mechanics that may need more than standard.

“Have a Harley with fuel injection that I sent to the UK,” began a reviewer. “It took over seven weeks to arrive and it cranked up the first time and ran with no problems. Love this stuff for long-term periods of time sitting without cranking up.”

Fuel type: All grades of gas

Gallons of fuel treated: 32 gallons

Best Long-Lasting Fuel Stabilizer—B3C Fuel Solutions Ethanol Shield Stabilizer

Most fuel stabilizer options stabilize fuel for up to a year or two years, but B3C’s stabilize fuel for three, really extending the life of fresh fuel. This strong formula has two additional components: antioxidants and a corrosion prevention system that works with all metals.

Some engines may also need higher octane fuel as they get older—this stabilizer is made to prevent that. And its lubricating texture is helpful for the functioning of upper cylinders.

“This is the best stabilizer I have used,” began a customer. “Had put it in my Honda power washer four years ago and finally had a real purpose to get it out again and I figured on rebuilding the carburetor. No way she started up on the first pull couldn’t believe it.”

Fuel type: Ethanol-based gasoline

Gallons treated: 240 gallons

Best for Worn Down Power Tools—STA-BIL Fast Fix Small Engine Treatment

A smaller fuel system will get a lot from this fast-acting STA-BIL fuel stabilizer. Its size of it makes it an ideal portion for toolboxes and back-ups in garages. It works best in the gas tank of smaller machines like mowers, blowers, throwers, and generators.

This is a great antidote for rough idling engines, too, and prevents corrosion once it’s added to a fuel system. That being said, like any fuel stabilizer, it won’t fix old fuel. New gas will need to be added to a machine that’s not operating smoothly. That being said, it’s key for obliterating carbon deposits and gummy residue.

Many of the reviews emphasize how well it works with similar success stories of old machines getting a new life. “I had a snowblower that would never start for several years,” wrote a customer. “After using this product it started it right up and it has been running ever since.”

Fuel type: Ethanol blends

Gallons treated: 20 gallons

Best All-in-One Fuel Stabilizer—Royal Purple Max-Clean Fuel System Cleaner and Stabilizer

Royal Purple’s fuel stabilizer is actually three products in one. When it seeps through a fuel system (compatible with both gasoline and diesel engines), it helps keep fuel fresh, cleans out the components, and prevents rough, inconsistent idling.

It’s best suited for use in cars (2 or 4 cylinder) every 10,000 miles, but it’s just as capable of being used in fuel that’ll be stored for some time.

“I’ve been using this Royal Purple fuel system cleaner for years now and I’m very satisfied,” wrote one contributor. “My 14-year-old truck runs like new and I know this is a contributing factor.”

Fuel type: Ethanol blends

Amount: Two 20 oz. bottles

Gallons treated: 1 bottle per tank of gasoline (fresh)

Best Engine Restart Formula—Start Your Engines! Fuel System Revitalizer, Pack of 8

This isn’t a fuel stabilizer, per se, but it fits neatly in a similar realm. The STA-BIL revitalizer is meant for machines that are far past the point of stable fuel and may have engines that no longer run or start properly.

Like a fuel stabilizer, it’s capable of eating away at gummy, globby fuel, but it’s not primed to prevent degradation and keep fuel fresh for extended periods of time. After a thrower or mower has been dormant for some time, this can be sprayed directly into the tank to support start-up.

“I have an older Craftsman lawn mower up at a mountain cabin that sits for periods of time and is very stubborn to start—even cleaning the carburetor did not really help,” explained a reviewer. “I was going to trash it and buy a new one so I thought I’d try this stuff… The mower started on the second pull of the cord and ran like a champ. VERY happy with this purchase.”

Amount: Eight-pack of 2 fl. oz. each

Gallons treated: 1 can per fuel tank

Best for Diesel Engines—STA-BIL Diesel Fuel Stabilizer

Gasoline and diesel engines both require stabilizers if they sit for long periods of time. Diesel vehicles and tools that need old fuel to stay in working condition will get their money’s worth from STA-BIL’s diesel-specific version.

Aside from the general degradation of gas, this prevents diesel from getting dark and going bad. Similar to others, it’s equally as protective from corrosion, buildup, and sediment, too. Some stabilizers are fine when overused, but the same can’t be said for this one—just be cautious when reading measurements.

“I have used this product for over 30 years and year in and year out never had a fuel problem in the spring,” wrote a customer who uses it over winters. “I have used the gas stabilizer and the diesel stabilizer. Easy instructions for ratio-to-fuel in-boat.”

Gallons treated: 320 gallons

The Best Fuel Stabilizers 2023—Summary

Old gasoline can be saved for up to one year or more depending on the fuel stabilizer that’s added to old fuel. Professionals and car enthusiasts alike will appreciate the money, energy, and annoyance these products save and how much they can affect an engine’s power and start-up, and lead to less fuel waste.

To prevent phase separation or fuel oxidation in ethanol-blended fuel in a gasoline engine, B3C’s stabilizer (US27.99, Amazon) is a solid choice. A diesel engine on the other hand will appreciate the STA-BIL Diesel Fuel Stabilizer (US28.99, West Marine) fuel additive. To keep the fuel line healthy on a smaller machine, STA-BIL Fast Fix (US11.99, Amazon) is a worthy consideration.

Choosing the Best Fuel Stabilizer—Buying Guide

To prevent having to drain fuel or bad fuel from ruining an engine, fuel stabilization is key. By adding a fuel stabilizer, treated fuel can last longer and stay safe sitting dormant. But not all fuel stabilizers are created equal—here are several top products that are worth looking into.

We hope our review of the best fuel stabilizers has been helpful. For more suppliers of related products, including stabilizers, diesel fuel additives, and fuel oil conditioners consult our additional guides, or visit the Thomas Supplier Discovery Platform.

Bad Fuel Symptoms. Lawn mower gas stabilizer