Reviews of the 10 Best 4-Stroke Outboard Fuel Additives for 2023 (2023)

For any boater who has had the privilege of enjoying the perfect blend of engine and fuel additive, without the latter would almost always mean less than optimal tuning. It's like spaghetti and meatballs or mac and cheese. Can we really blame them for the way ethanol and carbon from most fuel products wreak havoc on engines?

This rings true even for those looking for something more specific, like the best fuel additive for 4-stroke outboards. With the correct setup, you'll be able to see the big difference it makes in your engine's fuel efficiency, preventative maintenance, and overall performance.

In case you happen to be looking for the same combination that is right for the money, reading my review of the top rated fuel additives might be all you need to do.

Top 10 Fuel Additives for 4-Stroke Outboards

1. Engine treatment with marine foam SF-16

A true classic, the no-nonsense use, performance and guaranteed results of Sea Foam make it one of the safest options for sailors.

This product served as my sweet introduction to the wonders of fuel additives. Then I was intrigued by the brand's claim that you just need to add it to your gas or diesel fuel. It's basically a pour-and-go setup.

It's safe to say that I got more than I expected. I have seen the huge difference it has made on my already fuel efficient Yamaha outboard. This 4 stroke outboard gas has further increased my fishing boat's MPG by as much as 3 miles to be exact. As a regular angler, this is always a welcome bonus for me. This oil treatment allows me to cover longer distances and brings with me numerous benefits.

I also noticed that it took care of the occasional rough idle that I used to experience. I admit it's a pretty old engine, 4 years already. Even so, I bet it was more of a dirty fuel injector problem and this product fixed it after the first tune up and cleaning. I made sure to add it with every full tank to improve performance.

2. STA-BIL 360 22240 Marine fuel stabilizer

The right outboard fuel additives should be easy to use as they can provide all the benefitsfuel stabilizers. If I could name one good example of a product that deserves that label, the STA-BIL 360 marine is often the first that comes to mind.

I cannot completely avoid ethanol fuel products for my boat, with the vast amount of these products on the market. The good thing is that there are ready-made solutions for the said problem, and this fuel stabilizer basically solves it directly. For the amount of expensive damage ethanol can do to my boat's outboard motor, this is practically the more economical, long-term route.

It also kills two birds with one stone as local, extreme weather in the southeastern US where I live can also contribute to the damage. I have been using the one gallon version of this product for quite some time now and I have yet to see any signs of corrosion.

Maybe I'm used to it by now, but I can safely say that my charter boat's 4-stroke engine runs cleaner and quieter compared to other boats I've ridden. In addition to the smoother performance, I also get more gas mileage, although it's only a subtle difference (about 2 miles more) based on the little test I did. Even so, this convenience is one of the main reasons why I can no longer live without great outboard fuel additives.

3. YAMAHA ACC-RNGFR-PL-12 gorivo additives

This Yamaha concoction is a powerful cure for the ills of a 4-stroke outboard, and can revive it like a strong caffeine boost in the morning—only it lasts longer.

I purchased this fuel additive after my 9 year old 30hp Yamaha outboard started showing signs of sputtering. It took almost three visits to my local garage before I realized that I shouldn't have been too eager to follow every mechanic's advice. I browsed the net for a few days after the problem remained unresolved, and long story short, that trip led me to this product after several recommendations.

I was drawn to the fact that it was made specifically for 4-stroke engines. Ultimately, I will always give him credit for solving the idling problem that my boat's engine and I had been suffering for almost a month. I'm more than willing to shower praise on products that need time to flesh out their capabilities and, more importantly, deliver what they promise. Minemarine enginenever sounded this smooth in a long time.

I also noticed a significant improvement in my bowl speed after the first few bottles. Unfortunately, I can't say much about the supposed protective abilities it has since I've only been using it for 3 months. However, since we are talking about such an established brand as Yamaha, I am confident that it is doing a good job in this regard as well.

4. Star Brite 14308 Star Tron Enzyme Fuel Treatment

Cost-effective and more affordable, Star Tron's additive is a must-have for anyone looking to get the most out of their fuel and hard-earned cash.

This basically consumes the ethanol that may be present in the gas you are using. Of course, that's a good thing because my marine fuel went bad after only two weeks, so it didn't damage the engine. You can only imagine the money I save by relying on this neat fuel treatment, which extends the life of my fuel up to 2 years.

I have found that it works well with meerschaum, especially when maintaining the quality of the gasoline for my boat. Even when I leave the boat idle for a few months, it immediately starts on the first crank as if I had only used it yesterday. I attribute the longer fuel life mostly to my decision to combine it with the sea foam as I don't get the same longevity when using either one alone.

I also use this to replenish old, extra fuel that I usually store when I don't have as much time for fishing and boating. I even found it ideal for my lawnmower and chainsaw. More importantly, I can confirm that it works best for my boat's small 4-stroke engine, as evidenced by the stable performance I get every time.

5. Yamaha ACC-RNGFR-PL-32 Outboard fuel additive

For anyone with a 2-stroke or 4-stroke outboard from this brand, look no further than Ring Free. It's their power juice.

I thought the only logical thing to do was to buy this for my 5 year old Yamaha outboard when it started showing signs of hesitation issues. Admittedly, I wasn't a fan of the price, and this is coming from someone who typically exceeds 70 hours of active sailing time each season. It's a once or twice a summer purchase though, so no big deal.

Going back to the problems it solved, it has pretty much solved all the ethanol problems I've run into suddenly when the usual signs show up. I usually go the shock treatment route and pair it with seafoam when I use this mix, and it always gives good results. The engine started to run quietly and the air grills and filters stayed clean and worked like rain.

Idling at low speeds has become smoother. I have also found that I no longer need to change the spark plugs, even if I shock the engine as long as I use this seafoam additive. By the way, I also recommended this additive to my fishing friend who happens to have a 15 year old motor, and he got mostly the same results.

6. Merkur 8M0047920 Quickare fuel treatment additive

Anyone with a Mercury outboard should listen to the dealer's recommendations and opt for Quickare's timely solutions to most ethanol-induced outboard problems.

The primary strength of this fuel additive lies in its uniqueness in its brand. It may not be as versatile as other options like sea foam, but I wouldn't trade it for any other treatment if I had this brand of outboard. Almost every applicable boat I've used this on, either mine or owned by someone I know, solves all the common ethanol and deposit problems.

I always appreciate a safer option that meets the manufacturer's recommendations for the additives I use for the 4-stroke outboards. I'm glad I won't have to have that dilemma when I need it for anything made by this brand. I get smooth performance from my outboard and a sound that is just music to the ears of any consummate boater.

I haven't tried it on other brands of outboards, but I have a friend who can confirm that it works better than STA-BIL. This is also proven by some feedback on Amazon.

7. Star Brite Star Tron Enzyme Fuel Treatment Concentrate

Any boater who has perennial problems with ethanol gasoline, among which are not only expensive engine repairs and short fuel life, should know that he can find a reliable partner with this additive. It provides a host of benefits rarely enjoyed by boaters who rely on fuel additives.

For one thing, I rarely get at least two to three years of extended ethanol and gasoline life every time I put it in my fishing boat's 4-stroke outboard. I even use it for all other vehicles with small engines, especially if I have no choice but to use ethanol. I have been using it for almost three years on my boat and have yet to notice any damage to the entire fuel system.

I like that it saves me the hassle of regularly cleaning the carburetor. Any time saved as a direct result of the product's effects is gold to me. Moreover, I hardly have to pull more than once to keep the engine running like new as long as I use this additive.

I think it is important for the brand to start paying attention to the design of the bottle. I completely agree with other users who complain about the amount of spillage almost every time I try to pour this product out of its one gallon container.

8. Mercury 8M0047931 Marine Quickleen

Mercury's Quickleen proves the point that it is infinitely better and safer to opt for specialized formulations made for marine engines in most cases.

I used to use a number of fuel additives and stabilizers for my 4 stroke outboards. However, few products are as reliable and adaptable to specific vessel problems as this formulation can solve. I still use it for most of my outboards, 2-strokes and 4-strokes of various horsepower, and let's just say it has saved me numerous trips to the mechanic.

I have used this to solve my hesitation and misfire problems. Even when I wasn't very knowledgeable about cleaning injectors, I remember just pouring this into one of my speedboat's 100hp 4-stroke outboards and it solved the problem in no time. I would definitely use this first before committing to any permanent changes like replacing the plug and coil to save myself unnecessary expense.

In most cases, I've found that you just need to be patient to see results, especially if you want a pick-and-span fuel system. I've tried it on Yamaha and Mercury outboards and got the same benefits as any other fuel stabilizer, if not more in terms of money saving benefits.

Can't say much about the brand's claim of extending spark plug life. However, I can confirm that I rarely have to replace it unless I shock the engines, which is not very common.

9. Quicksilver 858080Q03 Power Tune

This neat spray could magically solve any carbon-related ailment your outboard might be experiencing. A good dose is often enough to get my engines back in top condition.

This product saves me from relying on the usual shock treatments to remove any excess carbon in the carburetor of my Evinrude outboard. I love that I really only need to spray it on the carburetor to get the job done. Of course, I still need to use up all the old fuel, but it almost always makes a big difference in starting the engine and running later.

This has since become my go-to carburetor cleaner for my 4-stroke outboards. Where others have failed to remove all that stale, old gas, this one proved to be the exception. The moment I sprayed it for the first time and those trademark foams appeared, I knew I had made a wise choice. Almost any part of your fuel system with carbon buildup will benefit from this powerful spray.

The opposite only means expensive disassembly, which I'm glad I can postpone or avoid with the help of this product. It not only saves money, but also a lot of time and effort. Sometimes I even just soak one of my engine's carburetors with this solution overnight and get the same results.

10. LUCAS LUC10013 Fuel treatment

I use this product as a fuel treatment when I want to save money to improve the performance of my outboard and get the most out of my fuel. Profitability is written everywhere.

Considering the cost of a gallon of fuel additives on the market today, this LUCAS fuel treatment is a godsend. That's almost guaranteed performance gains and long-term fuel savings for less money. I travel 50 to 70 miles while cruising and based on my tests I get a slight but no less significant increase of no more than 2 MPG with my boat.

It doesn't matter that I can use it for my trailers as well. I no longer go without this product because of the way my outboard runs smoother and quieter. I can always hear the difference when I use this and when I don't, and I can say the same for my trailers.

I even remember one time I was riding in one of my friend's boats and the engine sputtered. It's a good thing we brought my trailer where I keep a supply of this excellent additive. Long story short, we added this stabilizer to the outboard before we filled it with fresh gas, and after about two miles of coughing the engine up, the problem went away completely.

Driver for buyers

Your purpose for using the additive on your boat's 4-stroke outboard should be one of the main considerations when deciding on the best type of product. Do you want to solve the problems commonly associated with ethanol in fuel? Or just want your gas to last longer and improve engine performance? Maybe you want to decarbonize your boat?

As my review of fuel treatments, cleaners and additives can attest, these products do not have the same benefits, at least in certain cases.

Some choose to specialize in marine engines, while others are more versatile and can service a number of vehicle types and engine sizes.

It's safe to say that you should keep these exact benefits in mind and know if they apply to your exact situation or meet your specific needs. In addition to this important factor, it will not hurt to look at these areas:

Fuel and engine compatibility

Double check that the additive matches the brand of your 4-stroke outboard (eg Yamaha outboard additives) and the type of fuel you use with it. Each product should tell you which species it works best with. If this information is not readily available, be sure to check with the manufacturer.

Ease of use

Practicality should not be neglected. Does the product require you to take extra, complicated steps just to reap its benefits? How is the bottle designed? Does it help you take accurate measurements so you can pour a precise measure with every gallon of fuel in the blink of an eye?

Duration of stabilization

If you want your fuel to stay viable for as long as you want, you need to know the products that can deliver. Of course, you should also take into account any seasonal changes that might affect this. Winter may make some stabilizers less effective, at least compared to their winter-formulated counterparts.

What is a 4 stroke outboard fuel additive

Sea Foam is the most popular, the safest, and what I would recommend to anyone still trying out fuel additives for this type of engine. More or less, it provides all the great benefits your 4-stroke outboard can get from fuel additives.

However, I can say the same for a few of the other products listed here. Each has its own strengths, especially in the amount of money I save with their help and the engines they work best with. For this reason, I recommend them to everyone.

Is meerschaum safe for 4 stroke outboards

Not only is it very safe, but it is also easy to use and recommended for most 4-stroke outboards. The brand itself confirmed this on its main website. You can always pour directly into the container without any problems. Most boaters use it to quickly repair their boat engines when they have problems with carbon build-up. This is usually achieved by proper shock treatment.

Which is better seafoam or STA-BIL

If I'm going to consider adaptability in the many situations that 4-strokes find themselves in, I'd say the Sea Foam is the winner. The rule of thumb is that meerschaum works better with smaller engines that are more likely to be exposed to moisture, while STA-BIL is the exact opposite.

However, both are household names for a reason. I have found that the STA-BIL is ideal if you plan to keep your boat idle and maintain its fuel for long periods of time, given the wayworks like antifreezewhen it stabilizes its fuel.

Conclusion

I hope with the above information you now have a good idea of ​​what fuel to use in 4 stroke outboards and their ideal additives. To me, the best 4-stroke outboard fuel additive is one that consistently delivers everything you need while helping you save money, time, and effort while driving.