10 Best Ethanol Treatments for Outboard Motors of 2022

In spite of the rare privilege of being provided with consistent ethanol-free fuel, you will always have to be cautious about the potential long-term problems ethanol can cause your vehicle. As the old saying goes, it’s unavoidable for many people, especially Americans. We get that it’s environmentally friendly, but its disadvantages can be tough on the wallet.

There is nothing the best ethanol treatment for outboard motors can’t handle. From misfiring to idling, to low fuel longevity, it didn’t take me long to believe in these additives and stabilizers.

Below is my review of ten fuel treatment for ethanol products that stand out to me in all the time I’ve used them.

Top 10 Ethanol Fuel Treatment Reviews

1. STA-BIL 22240 Marine Ethanol Treatment

STA-BIL 22240 Marine Ethanol Treatment

The main benefit of STA-BIL 360 is that it anticipates boaters’ habits while also addressing ethanol problems.

However, despite its obvious advantages, I cannot back up the brand’s claim that it makes fuel last up to a year. That being said, I’ve only ever kept my vessel idle for 8 months at a time. Despite the length of time that I tossed the rest and refilled, my STA-BIL-treated gasoline still powered my Yamaha fishing boat efficiently for a day. I wouldn’t mind that perk.

For this reason alone, this brand will always be my go-to for keeping fuel fresh for a long time. Of course, that assumes you won’t be taking your boat out for a long time since it works better if you don’t disturb it.

In my case, it works best on small engines and outboards. It also works well as a fuel cleaner for my lawnmower, as I haven’t encountered any ethanol problems on any of the motors I have used it on. I also use it on my lawnmower every once in a while to ensure it starts smoothly every time.

I only have one small complaint about the bottle design. I wish I could pour directly without worrying about spills. I hate sometimes using a syringe to ensure accurate measurements and avoid spills.


  • Excellent fuel-keeping ability
  • Works best on small motors
  • Great fuel cleaner
  • Delivers most of what it promises


  • Bottle design needs improvement

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A ethanol fuel treatment or fuel additive should not be considered as a cure-all for ethanol issues. Phase separation cannot be guaranteed with every use of ethanol fuel. Nevertheless, what I can say is that this product made a big difference in how rarely I now encounter the performance issues I used to encounter with my boat’s outboard motor and other small tools the moment I started applying it.

2. STAR BRITE Star Tron Enzyme Fuel Treatment

STAR BRITE Star Tron Enzyme Fuel Treatment

Star Tron’s versatility is further enhanced by its myriad benefits associated with the use of ethanol treatments on most vehicles, including cars, motorcycles, and boats.

As far as fuel stabilizing goes, I think this product is right up there with STA-BIL. My father agrees with me as he uses it regularly for his Boston Whaler.

Even after more than a year of dormancy, his boat still starts and runs well. It may not be two years as the brand claims, but it’s still pretty remarkable.

Additionally, one of my friends used it on his pontoon boat for three years without touching it! He couldn’t get rid of the old gas, so he just applied this and refueled the boat with fresh 91 supreme gas. It started cleanly and worked as good as new for the entire day we cruised on it.

As someone who has used a few products that don’t boost mileage, I didn’t buy the mileage-boosting claim at first. I became a huge fan of this when I started seeing noticeable increases in MPG, starting at about 2.5 extra miles for my car. Since I never change my driving habits and save more in the long run, I’d take those seemingly marginal mileage jumps any day.

For me, it improves almost all vehicles and lawnmowers that I spray it on, which is a good sign that it deals with the usual ethanol problems. It’s not hard to hear the difference just by listening to it.

I would appreciate if it included a measuring tool of some kind. It would save me time and effort.


  • Proven to boost mileage and fuel efficiency
  • Works well for a lot of vehicles
  • Remarkable fuel keeping
  • Improves engine performance
  • Well worth the money


  • Needs a measurer

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With its combination of benefits, this product sets a new standard for boat and vehicle ethanol treatment.

3. Sea Foam SF-16 Motor Treatment

Sea Foam SF-16 Motor Treatment

Among ethanol fuel additives, Sea Foam is one of the few that has earned the trust of hundreds of mechanics over decades of use.

Almost always, ethanol issues take a backseat to where this product is applied. This is the product I use on boats, cars, lawnmowers, and leaf blowers, especially if I have no choice but to use ethanol-laced fuel. Some engines don’t perform as well afterward, but I can say that for the majority of them.

From someone who knows what ethanol causes poorly running engines to sound like, this product fixes the problem right away and prevents it from returning. Is it any wonder so many people keep using it?

It works better as a fuel cleaner than a stabilizer, in my opinion. It cleans up deposits in cars and gadgets that work well with it quickly after just pouring the right amount in a tankful of gas. However, I admit it’s a better stabilizer for most small engines, since my leaf blower still runs smoothly after storing it for 7 months.

However, it can’t work its magic on other outboard brands that I own. This is its only real flaw.


  • Can be used on a variety of vehicles and home tools
  • Easy to apply most of the time
  • Protects most engines from ethanol problems
  • Excellent fuel cleaner
  • Good stabilizer for small motors


  • May not work on certain gas or diesel engines

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There is no guarantee that Sea Foam will work with all engines. Although it can’t always deliver its powerful advantages, many in the automotive and boating industries are grateful that there is always this solid additive available on the market to prevent problems with ethanol.

4. STA-BIL 22275 Ethanol Treatment

STA-BIL 22275 Ethanol Treatment

In the end, it’s the difference it makes that seals the deal for STA-BIL 360’s special ethanol treatment solution.

It addresses ethanol issues just as well as Sea Foam while still guaranteeing your gas won’t be rendered useless by the same chemical within a month. That’s what makes it different to me. For my small engines to remain free from ethanol contamination, I could easily substitute this for the said fuel cleaner.

While I can get more out of other STA-BIL products when keeping my fuel fresh for a long time, this one still does a fine job in that it works well for gas or diesel you’ll be storing for no more than 6 months. In my experience, it works best as a fuel cleaner and an engine performance booster on all boats and cars that I’ve used it on.

I have a buddy who attests to the fact that this gives him a whopping 50 miles more per fill-up, which is nothing short of amazing. For me, I can safely say that it does give my Subaru at least 10 to 15 miles more per fill-up. Since I rarely get this perk in my outboards with the other additives I use, I can’t complain since the MPG increase is marginal in my boats, around 3 miles at most.

As for cons, I don’t like that the product is pricey, so I won’t hesitate to purchase it if Sea Foam is unavailable.


  • Above-average fuel stabilizing
  • Proven to boost mileage
  • Improves engine performance
  • Overall excellent fuel cleaner


  • Pales in comparison to a few STA-BIL products
  • Pricey

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As shown in this STA-BIL ethanol treatment review, this product is yet another reliable offering from a well-known brand that has its own unique benefits.

5. Lucas Oil 10576 Ethanol Fuel Conditioner

Lucas Oil 10576 Ethanol Fuel Conditioner

The Lucas Oil gas additive for ethanol delivers no-nonsense results consistently as a fuel system cleaner and helps engines run smoothly.

As a result of this fuel conditioner, I have seen its effects on my cars, boats, a buddy’s jet ski, and lawnmowers, so you can see its versatility. I think that’s solid proof of how effective this is as an ethanol buster because they all have two common denominators: improved overall performance and smoother starts after application.

The deceleration of my car has dramatically improved after I cleaned and lubricated the injectors with E85. It’s much more responsive now after I brake, and it fixed the bucking issue I had with my Evo X. It’s the only treatment I did for it, so I’m sure it’s the one responsible for fixing it.

I’ve been using this regularly for 3 years with close to zero ethanol issues. I’m not sure how much credit it deserves, but I’m fairly certain it contributes to the results.

When using this conditioner, I would stick to cleaning and engine protection rather than using it as an ethanol fuel stabilizer like others.


  • Proven to work on gasoline-powered boats, cars, jet skis, and other applicable machines
  • Improves performance and helps engines start smoother
  • Budget-friendly
  • Provides active protection against ethanol damage
  • Excellent value for money


  • Doesn’t keep fuel from getting stale that well

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If your budget’s a bit tight or if your car can’t handle ethanol, I recommend this product as an ever-reliable ethanol treatment for gas.

6. STAR BRITE Star Tron Enzyme Fuel Treatment

STAR BRITE Star Tron Enzyme Fuel Treatment

You can expect both outstanding fuel stabilization and long-term protection against clogs from this version of the classic Star Tron enzyme fuel treatment.

It is a product I love because it delivers on its promise. It guarantees fuel freshness for two years. At least, I can say the same for my old fishing boat’s Mercury outboard when I had to take a lengthy boating break after an accident broke my hip.

It started cleanly on the first pull-start. There was no rough idling or gumming whatsoever from the moment I left it running for five minutes until I started cruising. Having depleted my entire tank for one fishing day, I refilled it with fresh fuel and poured in a bit of this additive. It was a snap to use, if I may say so.

The majority of my small engines no longer clog if I use this fuel stabilizer and cleaner. If that isn’t a hallmark of an excellent fuel stabilizer and cleaner, I don’t know what it is. Using this stuff will not restore old fuel, but it will clear gunk and keep your fuel as good as new.

While I can’t praise its price tag anytime soon, there is a minor con in that it only works on small engines.


  • Keeps fuel fresh for a long time
  • Easy usage
  • Great in addressing idling and gumming problems
  • Protects from clogs
  • Removes buildups


  • Pricier than other good stabilizers
  • Benefits limited to small motors and engines

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For fuel stabilization, I think this trumps STA-BIL, and I’m sure I’m not the only one who does. If I’m looking to store for a year or two, I’d easily pick this over STA-BIL.

7. LUCAS LUC10013 Fuel Treatment

LUCAS fuel treatment has a well-founded reputation for delivering results. I see it as simple as adding one ounce of this ethanol treatment to every five gallons of fuel to get that much-needed peace of mind.

As a result, I get, on average, 1 extra mile on my Toyota Tundra and another pickup truck when I use it on most of my land vehicles. Although both have plenty of mileage and are a bit older, I think it benefits cars with older engines, at least 10 years ago or more.

A workmate of mine owns a 2016 Camry and told me he tried it but did not notice any significant changes. Some report getting up to 10% more fuel economy, which I bet is very plausible. I’ll have to test it on other diesel and gas-powered vehicles to find out.

The fuel treatment works as a repellent for fuel injector problems and keeps the engine running like new, which is adequate considering I’m obviously only extending the engine’s life. Other fuel treatments haven’t done the same.

When I use my ratio of application, I am able to save 8 to 10% on fuel, and that’s not even counting the protection that essential parts like injectors and fuel pumps receive. Because these parts are prone to wear and tear courtesy of everyone’s favorite old buddy ethanol, I’m sure I’m saving a lot of money.


  • Decent mileage and fuel economy improvements
  • Ideal for preventive maintenance
  • Cost-effective and great value for money
  • Keeps gas and diesel engine running at peak condition


  • Minimal benefits for vehicles with new engines

8. K-100 K100-G Fuel Treatment & Additive

K-100 K100-G Fuel Treatment & Additive

Almost anyone who uses K-100 will discover how much of a gem it is for phase separation and fuel cleaning.

On my Yamaha outboard, lawnmowers, snowblowers, and motorcycle, I have tested this out. While I’d refute the brand’s claim that it “eliminates water”, I can say that this is one of the top-tier fuel treatments for phase separation problems. Water isn’t eliminated, it’s burned off by the engine.

As a result of it, I can report 30 extra miles with a 10 ounce application per 20 gallons application, and that is what convinced me of how great this product is. That’s exactly how many miles my 2008 Infiniti can run, and I can attest that it doesn’t lie on the mileage meter.

For my motorbike, I can say the same, especially if I regularly use ethanol-rich fuel. The motor sounds like music to my ears every time I take it out for a ride, and it gives me at least 10 more miles. In my opinion, it makes a big difference, though I’m not much of a biker.

As for my outboard, I’m glad that it fixed a lingering problem it had with starting. The motor starts fine, but it dies after about 15 seconds. I tried K-100 on it and let it sit overnight. The following day, I gave it a pull-start and the problem never returned.

In addition, I wish it included a funnel to make it easier for bikers, who are its regular users.


  • Best for addressing phase separation
  • Remarkable mileage boosts in cars and motorcycles
  • Improves engine
  • Versatile


  • Pricey
  • Could use a funnel for motors

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With just that alone, this fuel cleaner is already a winner. Your standard ethanol additive in gasoline is rarely able to match its mileage boost.

9. B3C Fuel Solutions Ethanol Fuel Treatment

B3C Fuel Solutions Ethanol Fuel Treatment

Considering my positive experience with it, I can attest that it really does function as a “Mechanic in a Bottle”.

I usually get two-stroke and four-stroke outboard problems, so it’s a great solution. Despite the fact that Sea Foam can almost magically dispel idling and sputtering, it’s a good alternative, especially if you don’t have enough stock. You can always turn to this treatment for your ethanol problems.

As long as its fuel is compatible, I won’t hesitate to use this on anything with a carburetor. Using this fuel cleaner cleared up a clogged carburetor that my generator has been having for more than a year, and I am glad to report that it is the first fuel cleaner I have used that has worked. I am happy to let you know that the generator has been running well lately.

This should be applied to almost any vehicle or machine that has sat idle for over a year. I can compare the performances of my untreated and treated snowblowers.

This product is expensive, considering its price, bottle contents, and recommended doses per gallon. However, it’s a better deal than other lesser-known brands.


  • Suitable for outboard motors and generators
  • Solves sputtering, idling, and rough starts
  • Cleans carburetor buildups
  • Great for restoring the performance of small engines


  • Costs more

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10. Opti-mizer Ethanol Fuel Treatment Stabilizer

Opti-mizer Ethanol Fuel Treatment Stabilizer

I feel that this stabilizer is not getting the recognition it deserves. It works great on 4-stroke motors, so if you have been struggling to find an ethanol fuel treatment for that type of engine, I strongly recommend you give this one a try.

As a result of my testing this fuel treatment out on Mercury 2-stroke outboards, a Yamaha 4-stroke outboard, a riding mower, and an ATV, I am able to say that I get the best results with 4-stroke engines. By best, I mean that the engine runs cleanly and almost like new.

There isn’t as much of this advantage with the other motors and vehicles I mentioned. However, the fact that I don’t encounter the usual tell-tale signs when starting them serves as a good hint that it is at least exerting a positive effect to some degree. I think it is a great carburetor cleaner for this reason.

This keeps my riding mower fuel fresh when I won’t be using it over the winter. It keeps fuel from going stale for longer than 6 months, the longest I’ve kept them idle. When I started using it on my 4-strokes, they didn’t display any of the common snags or slipups.

The 4-stroke limitation serves as my main gripe with this fuel stabilizer. Although I understand that they have a separate product for it, there are many brands that formulate fuel stabilizers for both 2-stroke and 4-stroke engines. However, if you need to treat other engines, it isn’t cost-effective.


  • Proven to work great on 4-stroke engines
  • Keeps fuel fresh for more than 6 months
  • Cleans carburetors
  • Shows active protection against ethanol


  • Outstanding benefits are limited to 4-stroke engines

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Its focus on small 4-stroke motors alone makes this Opti-mizer stand out. I challenge you to name another brand that can deliver the same results.

Buyer’s Guide

Fuel stabilizers and fuel treatments are sometimes used interchangeably, but in essence, they may serve different purposes. Before purchasing fuel treatment or fuel stabilizer, you should understand their differences.

Fuel stabilizers such as ethanol fuel treatments are mainly focused on enhancing engine performance rather than storing fuel. Their purpose is to prolong the engine’s life rather than keep fuel at its best. However, that doesn’t mean that they’re completely devoid of benefits related to fuel longevity. Brands formulate their solutions with overlapping advantages in mind, after all.

It’s logical for you to choose products that solve that specific issue. In order to choose products that are specifically marketed as an ethanol gas treatment for small engines, you should pay attention to their compatibility and specificity. Then, read the user reviews of these products.

Ethanol treatments that are effective are those that clean the fuel system thoroughly and boost engine performance. It should be able to deal with phase separation and break down sludge buildups that cause ethanol damage.

Ask the manufacturer about its suitability if you are using E85, E10, or another type of diesel or gasoline. Even the age of your motor should be considered.

If you aren’t switching from ethanol to non-ethanol, knowing what ethanol treatment to use would be beneficial to your wallet and engine.

What is the Top-Rated Ethanol Fuel Treatment

The best options are STA-BIL, Sea Foam, and Star Tron. Star Tron’s Enzyme Fuel Treatment tackles ethanol fuel issues directly, and it has hundreds of satisfied customers to back its claims up. In addition to addressing many ethanol problems, the other two are also a great choice.

Even if I highlighted those three, I wouldn’t ignore the other brands and products featured here. They have also demonstrated the ability to beat ethanol despite being not as well known.

How Do Ethanol Fuel Problems Affect the Fuel System

The term “phase separation” is all you need to understand how ethanol damages engines and motors. Ethanol tends to absorb water naturally found in gasoline and diesel. This results in this separation.

Whenever fuels have completely undergone phase separation, they have a higher chance of damaging integral components of the engine and fuel system, including carburetors and injectors. To keep the fuel system running, the fuel would have to be drained if this is the case.

Also prevalent are clogged fuel systems, in addition to gasoline turning into varnish as a result of corrosion.

Does Ethanol Fuel Treatment Work

Certainly, and most of the products in this list are capable of doing just that. In the end, these products prevent ethanol damage as long as they prevent phase separation by either absorbing water or burning it off before phase separation occurs.

Does Sea Foam Stabilize Ethanol Fuel

Sea Foam will always provide some measure of ethanol protection, but I cannot guarantee that it will be effective on all types and ages of engines.

The bottom line is that Sea Foam is a good fuel stabilizer, especially if you want to deal with ethanol issues. However, it is not as effective at keeping your fuel viable for extended periods of time.


Having done some trial-and-error myself, I am able to back up the numerous claims of other satisfied users. Based on my experience, it’s any product that keeps engines running as they should. In short, it should work. With this guide, I hope that you will not have to waste too much time and effort finding what works for you.

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