I am looking for an all in one fuel additive for my Mercury 115hp four stroke. I would like one that works as a stabilizer, lubricant, cleans injectors, and ethanol issues. Looks like there are a million options out there and each does certain things, but would like to find an all in one, if there is such a thing. Any suggestions, and/or what do you use?

Thanks in advance for any advice.

Marvel Mystery oil

I like the Lucas products.

I've use Marvel Mystery oil for the past 50+ years

Marvel Mystery

You don't need fuel additive. Save your money

seafoam is the best all around.

I run 2 big cans thru the f150 every 2-3 months, keep it in the boat gas and all our sxs/4wheelers. the stuff works.

Actually if you let gasoline sit for a couple of months, the ethanol will separate from the gas, it's called phase separation. When THAT happens, the alcohol will absorb water vapor, and sink to the bottom of your tank. When that happens, you're not getting fuel, you're getting water saturated moonshine.

I run Sea Foam in mine. Usually the recommended maintenance amount throughout the year just to insure the fuel system on my FI 4 stroke stays clean. In the rare instance fuel sits in my tank more than 2 months I will drain it completely and refill with fresh, and add a liberal amount of sea foam to it as well. Phase separation is real. I make no claims to sea foam being a stabilizer, it certainly isn't advertised as such, but I have seen the benefits of its ability to remove carbon build up in my old 2 stroke and several other engines (large and small). For me there is no downside to using it and it's cheap so no real reason not to.

I ran ring free in my Yammy F70 when it was still in warranty, just because that's what Yammy wanted. But stopped that as soon as warranty ran out and went to Sea Foam, several years later, no problems.

Pat,

You are exactly right. The ethanol they add to some of our fuel is the problem for the most part. The next thing is how fresh the fuel is. For my boat and all my yard equipment I buy that no alcohol fuel, but I make sure where I buy it, that they sell enough to keep it fresh.

Then I make sure I don't leave the fuel in the boat to get old either. It gets over 45 days old you don't want to run that in a motor that you would have the throttle at 4000 rpm’s or more for any length of time. If I don't keep the fuel in my boat used up when I come back from the lake and it sits there for more than 3 weeks, I pump it out and put it in my truck and or the wife's suv.

That way I can add however much I think I need when I am going to the lake, after all I don't always need to fill the boat fuel cell. This way it's as fresh as possible and I do like to add a fuel additive, Seafoam is one of the best jimo. I prefer the stuff Yamaha has, it's called Ringfree Plus, now days, it's expensive and it's hard to find in my area. I get it from boat.net... They have it in 2 different sizes, I get the quart size bottles and I keep 6 to 8 quarts here at the house. You add 1 once of it per 10 Gallons of fuel.

This stuff not only helps keep your engine clean but it also helps keep the fuel fresh and clean. My Toyota Tacoma 4.0L loves this stuff also, helps keep the catalytic convertor on the exhaust system cleaner as the fuel system and engine also.

Now do you have to buy this stuff, no. I just flat not run any other fuel in my boat or lawn equipment other than the no alcohol fuel period. And yes I do put 1 once of ringfree to every 10 gals of fuel. I use to work on this stuff professionally, I am retired now, but I have seen the insides of the engines that had this product and those that didn't. There is a big difference. Just say'n...

seafoam is a stabilizer, at least it says it is on the can. been using it a long time and never had a problem with my fuel.

Seafoam is nothing but a mixture of light oil, naphtha, and isopropyl alcohol. It's the alcohol that cleans the carbon off your pistons. You know what else cleans the carbon off your pistons. Gasoline with ethanol.

Yes, that is true but that stuff in the fuel also causes pre detonation which just eats away at the top of the pistons and really gets focused over on the edge of the piston going out the exhaust port. Heck just plain water sprayed into the combustion chamber knocks all of the carbon off. Drag racers have done that for years, but not to clean the carbon out. You will get a compression jump when the water flashes off.

It's more about how the better chemicals removes the carbon and more importantly keeps it out. Then all those chemicals and how they mix with the fuel, or in some cases how it doesn't mix so well. It will cause the combustion to sky rocket and that alone causes a handful of other things to weird out.

You can use this blue Def that all the new diesel engines use, they are basically doing that with it. Google search what blue Def is, you get right down to it, it's animal urine, so you could just do that in your outboard if you like, it will knock the carbon out for sure, it just doesn't do it so easy on the cylinder bores, and of course all the bearings are being lubed by this mixture if it's a two stroke.

I am just say'n what I do with my stuff and what I have seen over many years and many many powerheads.

As you walk down this dark path of junk fuel and low tolerance motors the need to keep everything fresh is critical.

Ok you’re listening. Good.

Your new direct injected motor is designed to run ultra lean. That’s how it gets its economy. When everything is good, no problem. Now that gas is a few months old and it’s starting to separate. When that happens the oil from the injector doesn’t saturate in water or alcohol. When that happens the precious oil doesn’t get into the places it needs to be. Usually that’s your rings. The fuel/oil mixture is not only lubricant it’s also a coolant.

Now that ring gets super hot. So hot that when the cylinder loads its fuel charge the hot ring will ignite the fuel before the plug fires. When that happens the rods and crank can’t handle the pressure and it will grenade on the spot.

Built up carbon will do exactly the same thing.

So a few bucks to keep your fuel good is really cheap insurance.