Better Boater: Are fuel additives worth your time and money?

Snake oil. We’ve all heard the phrase. For a lot of people, the phrase “fuel additive” may as well mean the same thing. We decided to do a little sniffing around to see if that’s actually the case. To get to the bottom of this, we need to look at the reason people want to use fuel additives in the first place. That reason, as you may have guessed, is ethanol.

“Ethanol” is a dirty word in boating circles. The problem is that in 2005 the government implemented the Renewable Fuel Standard, which mandated that all fuel sold at gas stations be blended with biofuels (usually corn ethanol). Because they assumed that gasoline usage would steadily increase, more and more ethanol got mixed with the gasoline. However, since that same year, our gas usage has actually decreased, but the ethanol mix kept rising. Boat engines are designed to function with fuel that has a maximum of 10 percent ethanol and are in fact prohibited from using fuel that has more than 10 percent.

So ethanol is bad and the only way to combat it is to get a fuel additive for your boat, right? Not so fast, cowboy. While E0 fuel would obviously be best, that’s not really an option anymore, so E10 is what we have. Plus, when it comes right down to it, E10 may actually be a better marine fuel due to its tendency to keep low levels of water moving through the fuel system, keeping things “dry.” That said, the onus is still on you, the owner, to maintain your boat properly. After all, proper, attentive maintenance will win the day over some one-size-fits-all miracle product. That being the case, here are a few ways to keep your engine in tip-top shape that don’t involve incantations to the boating gods.

Get Rid Of That Water

The most prominent boogeyman when it comes to engine maintenance (at least as it relates to fuel) is phase separation. Phase separation occurs when a sufficient amount of water enters the gas tank and causes the ethanol to physically separate from the gasoline, resulting in two or three distinct layers. A lot of fuel additives claim to get rid of the water and generally prevent that separation, but that’s not actually true. In a webinar in 2011, Mercury Marine revealed their findings about what happens in phase separation and how to prevent it. According to Mercury, “Major multibillion-dollar companies with enormous resources have improved gasoline additives but there have been no recent breakthroughs involving 'magical technology.' Claims made by companies about 'space-age,' 'revolutionary,' or special proprietary technology should be looked at with a high degree of suspicion.”

No fuel additive is going to make bad fuel usable or reintegrate separated fuel, so there are really only two ways to prevent phase separation: have a full fuel tank or an empty one. That’s pretty much it. Obviously, with no fuel in the tank, there’s nothing to separate. Ethanol absorbs water, but it has to have water to absorb first. It’s not going to reach out and grab water molecules out of thin air. So preventing water from getting into the fuel tank is your best bet. Therefore, a full tank (or almost full—95 percent is sufficient, since you need to leave room for the fuel to expand a little) leaves little room for water to condense. Since marine engines are vented—unlike automotive engines—this is the primary way water gets into your fuel. If phase separation has occurred, the only way to fix it is to drain the affected fuel from the tank and add fresh gasoline. Interestingly, it’s common practice in the Midwest—where E10 has been the standard for over a decade—to always top off your tank.

Get A Filter

Now that we’ve established that ethanol doesn’t deserve (all of) its ill-gotten reputation, there are still a few things to keep in mind. The most important thing is that ethanol is in fact a solvent, and therefore dissolves resins, dirt and rust in the fuel, which will then head straight for your engine. So you gotta get a filter on that sucker. You also need to make sure you have plenty of spare filters and a galvanized bucket to keep the used ones in before you dispose of them. A 10-micron filter is what you should be aiming for. E10 sometimes also has a tendency to form a mysterious sludge-type substance that can mess up your engine and clog your filter. Richard Kolb, the manager of Emissions and Regulations for Volvo Penta, recommends switching to a different gasoline supplier if you run into this problem. According to him, there are 108 different approved compounds that can be used in gasoline, and any mixture of these can cause the sludge. Different suppliers use different mixes, so this can help.

Get Smart

What it all boils down to is using your head, both while maintaining your engine and when you choose what to put in it. Jerry Nessenson, president of ValvTect, a company that offers its own line of fuel additives, says, “Boaters need to be cautious about what they pour in their gas tanks.”

He suggests that the Oil Certification Committee adopt the same standards developed by the American Society of Materials and Testing for fuel additives in the automotive industry.

“Any additive manufacturer should be able to verify its claims via industry standard testing,” adds Nessenson. “It is disturbing that some companies have challenged this need.”

While there are certainly things you can add to your fuel that will help—such as a fuel stabilizer when the boat is going to be idle for long stretches of time—you just need to be smart. Think of it this way: would you drink some miracle cure-all drink your buddy whipped up in his labora—err, kitchen, without finding out what was in it first? Treat your boat’s engine the same way. Do your research first before committing to something that could be harmful down the road.