Fuel Additives: Snake Oil or Good Science?

Posted by By Darrell Nicholson at 11:56AM - Comments: (19)


As one who has spent many hours in exotic locations, cycling bad diesel fuel through a make-shift filtration system, I am as vulnerable as anyone to the promises of a quick and easy solution to fuel problems, which is one reason why Practical Sailor has delved so deeply into this topic.

In 2007, Practical Sailor warned of the problems related to ethanol-laced fuel (E10), and in 2008, we tested various products claiming to prevent problems related to ethanol and found varying degrees of success. In 2009, we looked at dieselfueladditives formulated to attack biological bugs that thrive in diesel. In the summer of 2012, we looked at gasoline additives, taking a closer look at the standards the industry is using to separate the snake oil from the elixirs. And earlier this year, we published an updated compilation of these articles as well as the first report, including our long-term study of fuel additives for storage. 

PS tested products that claimed protection from ethanol fuel's bad side effects.

While the ethanol problem has brought a mountain of headaches to boaters, it has ignited a booming trade in fuel additives. Way back in 2012, at the Miami boat show, I heard Gerald Nessenson, then president of ValvTect Petroleum Products (now retired), talk about the state of the finished fuel-additive industry and what established companies such as his are trying to do to fend off what he felt were unsupportable claims by small upstart companies.

Nessenson was quick to point out that the finished gasoline at our pumps already includes a range of additives that deal with issues such as corrosion, fuel oxidation, and deposit build-up. He added that the harsh marine environment presents special challenges and cited the well-documented ethanol-related problems in outboards as evidence that boaters need to be more cognizant of their choices when selecting, storing, and—if necessary—treating their fuel. But when it comes to comparing the fuel treatment products on the market, consumers are effectively left in the dark.

As Nessenson explained in his briefing on the topic: “Since there are no industry specifications for a multifunction gasoline additive for finished fuel, just performance tests that were established to meet refinery and engine manufacturer standards, a company can introduce products that do not meet any industry standard for components or testing for performance, long term incompatibility or engine damage that can occur after years of use.”

One of the biggest culprits, Nessenson said, were ethanol treatments that comprise alcohol, glycol, or new "space-age" technology “claiming superior performance to products that the world’s largest petro-chemical companies develop for the world’s refineries and engine manufacturers; but with no industry acceptable documentation.”

The most blatant offenders, said Nessenson, are those companies that claim to be able to restore phase-separate ethanol blends. Phase separation occurs when water in the fuel tank is drawn into the fuel until a saturation point is reached, at which time the ethanol and the water can drop out of suspension into the bottom of the tank. Ethanol-laced gas is more susceptible to this process than non-ethanol blends.

“Once phase separation occurs, there is no safe way to treat that fuel,” said Nessenson. “Engine manufacturers and gasoline refiners state that this is not possible, and if this is attempted, it could cause engine damage.”

In our 2009 test, only one product we tested, MDR E-Zorb, claimed to restore separated fuel.

As we continue on with our various studies into fuel additives, PS is interested in hearing about your experiences. We would be particularly interested in hearing about anyone having engine damage attributed to using a fuel additive or a warranty claim rejected on the basis of their using a fuel additive. If you currently use a fuel additive that you know little about, you don't need to panic.

Such damage typically would not be the result of a single use, but repeated long-term use. Our own testing with both gasoline and diesel treatments indicate that limited use of the most popular brand name products will not cause any harm, but how much good the additives actually do is tougher to measure.

We advise anyone currently using or considering using a fuel additive to first seek the advice of their engine manufacturer. It will be helpful to have some form of NMMA certification standards that make the process of comparing additives easier, but given the nature of this science, I expect we'll be trying to sniff out snake oil for some time.

Comments (19)

Have to agree with "evan's" post near the top of these comments.

"You haven't really offered any useful information to the reader In this article.

"I subscribe to Practical Sailor for the unbiased testing and reports but lately all I get are teaser articles like this with limited content and a link to an article or e-book behind another paywall.

It looks like I am paying for a subscription to advertising emails. Your business model isn't working for me... sorry."

Keep it up and I will not renew my subscription.

Posted by: webguy | July 4, 2018 12:52 PM    Report this comment

Here in Nova Scotia I always use high test for all small gas engines. As for my marine diesel, I only use a biocide. I use a Racor filter and pour diesel in by the yellow container, slowly. And I keep the tank more or less filled in the winter. Not to the top, because diesel expands.

Mike Casey
Halifax, Nova Scotia

Posted by: barrington | July 3, 2018 2:07 PM    Report this comment


You haven't really offered any useful information to the reader In this article.

I subscribe to Practical Sailor for the unbiased testing and reports but lately all I get are teaser articles like this with limited content and a link to an article or e-book behind another paywall.

It looks like I am paying for a subscription to advertising emails. Your business model isn't working for me... sorry.

- evan

Posted by: eheffa | July 1, 2018 10:49 AM    Report this comment

I find the subject somewhat misleading. This is not about fuel additives, it is about additives for gasoline.

With respect to diesel fuel, anyone who has had an algae bloom in a tank of diesel fuel, and subsequently run out of fuel filters because the "snot" plugs them as fast as they can be changed ... is a believer in diesel additives.

I had a "bloom" in close to 3000 gallons of diesel fuel on an 85' passenger boat I was responsible for. I've never forgotten it.

Kim Kimball

Posted by: KimKim | June 28, 2018 4:08 PM    Report this comment

Our long experience buying diesel and gas here and abroad is that water is the real culprit. So using commercial and home made filters when filling helps. As buying diesel always from high volume commercial users. And gas from land based big volume stations.
We haven't seen much benefit from additives. However, fuel firms in the NE routinely add additives in the winter to break up sludge. But fuel oil is much dirtier than diesel. In some parts of the world, e.g. Bahamas and Africa, dirty moisture laden fuel is routinely expected. So everyone uses commercial and home made filters. With outboards and generators routinely lasting many decades the home made filters seem to work.
Finally, the US Army, Navy and Air Force aren't immune to these problems either. So they run their engines fairly frequently with careful attention to filters. And test for water and content.

Posted by: Piberman | June 28, 2018 12:30 PM    Report this comment

At university decades ago, we tested diesel fuels for their ability to absorb moisture. Here are our observations:
Diesel fuel absorbs water.
As water is absorbed, volume of the fuel increases.
The diesel / water mix remained in solution up to about four percent depending on source and time of year.

Unfortunately, this 'fuel' turned a diesel engine into a steam engine. Although interesting in a lab setting, we saw no benefit to a water-saturated diesel fuel... since the water formed an environment for growth of bacteria and fungus.

Our conclusion:
Fuel polishing systems are required for low turn-over tanks.
Filters to remove water from diesel must be frequently purged to drain moisture. Allowing accumulated moisture to sit in the filter housing invited growth of bacteria and fungus, reducing effectiveness of the filter.
Temperature simulations showed little impact. Tropical versus arctic was not a substantial difference.

Posted by: Gramma | June 28, 2018 10:25 AM    Report this comment

Ethanol is hygrascopic, it draws in moisture from the air. Using E.10 in a marine environment, with high humidity where fuel often sits in tanks for long periods, is inviting problems. In diesel fuel, diesel sludge (microbial growth) lives in the water and feeds off the fuel. It sits in the bottom of the tank. Yes, right where the fuel feeds in. Over time the byproducts of sludge growth then spread through the fuel compounding degradation problems. As others have commented, even without the sludge fuel degrades and doesn't burn as well causing increased carbon, varnish and gum deposits and sub-optimal performance. Sludge in the fuel can easily block fuel lines, It is critical in sailing vessels when the engine is often only used for short periods or in emergencies and fuel tends to sit longer in the tank. Naturally, keeping fuel tanks full in a sailing vessel is more problematic.
Combustion byproducts of ethanol damage engines; the reality in my view is that's why content is limited to 10%. People will then think it's wear and tear, not the fuel. I won't use anything with ethanol in it, in any engine.
As others have testified, there is a lot of crap out there and I've been burnt wasting my money on them. The best product I have ever used is Pro-Ma DT-5 which is available on-line from www.marinefueloiltreatments.com
I haven't used all the products but the fuel treatments work (yes I'm a cynical grouch, - it took a lot for me to be persuaded).
The treatment includes a surfactant which allows water to mix with the fuel (hey, prevention vs. cure) and a detergent which is brilliant at keeping the fuel system clean. I haven't used the biocide so cannot comment.
I now use the gas treatment in my cars, mower and brush cutter. Have been for over 20 years and never had any problem with injectors, fuel pumps, filters. The mower and brush cutter are original 2 strokes, over 20 years later they still work fine and I'm yet to clean let alone change a spark plug.
For all boaties everywhere I'd suggest you run some tests, I'll be interested to read how they stack up.
By the way the grease is ridiculously good, particularly in a marine environment.

Posted by: The sheet hand | October 2, 2015 2:09 AM    Report this comment

Having owned a large marina and boat/motor dealership I can attest to the effectiveness of Yamaha Ring Free fuel additive. We rebuilt an average of 10 motors a month and it was obvious who used high quality factory oil and ring free additive or the equivalent motor manufacturer's product. No stuck rings and very little carbon build up. It is especially true today with substandard ethanol fuels coupled with non factory oils. All oil starts out the same, but ends up different based on the additives used.

I have run Cummins Diesels for years and had a bad algae problem in two boats. The problem was more pronounced up north because of the temperature change which produces condensation. Keeping your tanks topped off is important along with knowing who you are buying fuel from. I have had excellent results running Valvetec fuels and additives when their fuel is not available. I have had less success with Biobor, but living in Florida now and keeping the tanks topped has kept me out of trouble for 5 years with our current boat.

Posted by: douglas3246 | September 13, 2015 9:34 AM    Report this comment

There are many fuel additives on the market, but few fuel enhancers.
Shellbourne Fuels in Canada have been making racing fuels for automotive and marine engines; fuel enhancers for gasoline and diesel vehicle fleets for many years. They now manufacture both gasoline and diesel fuel enhancers for marine engines. These are the only EPA approved enhancers on the market and include a complete list of contents. Experience around my yacht club is noticeable performance improvement after use.

Posted by: George G. | September 9, 2015 4:24 PM    Report this comment

There is an easy method to determine if gasoline contain alcohol.
1. Find a tall skinny straight sided clear bottle. If you can get a test tube like those used in a chemistry lab that's ideal.
2. Fill the bottom 15 to 20 percent of the bottle with clean water.
3. With the bottle exactly vertical place a strip of tape on the outside so the top edge of the tape precisely marks the top of the water.
4. Almost fill the bottle with gasoline and cap it.
5. Shake the bottle vigorously for about 30 seconds.
6. Hold the bottle vertical and wait a minute for the gasoline - water boundary to stabilize.
7. If the boundary line is higher than the previously marked top of the water then there was alcohol in the gas. The alcohol has been pulled out of the gas by combining with the water to increase the apparent volume of water.

Posted by: JVB | September 9, 2015 1:43 PM    Report this comment

No fuel additive test would be complete without testing Ethanol Medic and Diesel Medic by Fuel Medics. these products remove the water chemically, clean injectors, stabilize the fuel, improve starting and performance. The Diesel Medic by removing the water in the tank eliminates the need for algae related products.

Posted by: Keyzcaptain | March 4, 2012 4:21 AM    Report this comment

Thanks to PS for taking this on.

The 8000 members of the Antique and Classic Boat Society are actively resisting the creeping "ethanolization" of boat gas, with roadside stations (but nor marinas) moving from E-10 to E-15 this year If you think there were a lot of deposits in the Atomic 4 tank on the Pearson 30, you should see what breaks loose from the tank walls of Chris Crafts, Lymans, Hackers, etc from the 20s and 30s. It has been such a problem that many members, including this one, have chosen to install new aluminum tanks, albeit with good filtration too.

In addition to the Unidentified Deposits that clog the fuel system, ethanol is widely known to also cause many of the various hoses and gaskets in these old boats to deteriorate and sometimes fail, causing dangerous fuel leaks. The school solution has been to replace all such material with modern alcohol-proof components - but too often after a member learned the hard way. It would be helpful if PS would identify the time frame in which most builders started using alcohol resistant components.

We have not developed any special expertise on additives. There is the usual range of opinion, with agreement only on the fact that, if you can't drain your tank for the winter, store it full usually with some additive, if there is ethanol about. Some members haul expensive av gas home to avoid ethanol. Others seek out ethanol free sources, only some of which are listed on such web sites as pure-gas.org.

We look forward to the results of your new test program on additives.

Gene Porter
Chair, ACBS Gov't Affairs Cte

Posted by: Oldwoodboats | March 3, 2012 12:27 PM    Report this comment

greetings from the Chesapeake Bay
Adding to the MIX : Google "fuel additive testing" .There are very few tests
out there . One from england that I recall .
E.W. Clucas

Posted by: Edward C | February 29, 2012 4:21 PM    Report this comment

Arizona has required 10% blended fuel(mtbe,ethanol,etc)by law for over thirty years.In my experience which includes autos,boats,atv,motorcycles,and airplanes there is nothing to worry about if you provide the most minimal of precautions such as don't let water accumulate in your fuel system.I've never in thirty years had a problem with a 2 or 4 cycle motor that was related to the use of alcolhol in the fuel.All this talk is much ado about nothing.

Posted by: RAY C | February 29, 2012 1:52 PM    Report this comment

I would love to have access to a source that would report the ethanol concentration in the different brands and grades of gasoline sold in the various states. Grant's comment above suggests I may be right in my preference for the highest octane gas I can purchase for all my two stroke and small engines, but I really have no idea what I am actually getting. Furthermore, I should report that I tried some additive I bought at Home Depot for use in an outboard, chain saw and leaf blower (I don't remember the additive brand), and it was so bad that I had to have all three carburetors cleaned. My mechanic told me the gas would not burn when dumped into a large pan and touched with a match.

Posted by: ERIC R | February 29, 2012 1:24 PM    Report this comment

It would be interesting to know, how biodiesel compares to the new diesel chemistry. So far bio diesel has a different chemical setup than regular diesel, and I am not aware of any regulation so far to add problematic chemicals to it. What I have experienced though has been a disaster by mixing biodiesel and the new diesel. Mixes we used to do, such as B20 or B30, we cannot do anymore. We had a quick buildup of tary sludge that, according to our observation as well as in our company provider's opinion, was not a biological but rather chemical reaction. We'd love to hear from you about this.

Posted by: HWI | February 29, 2012 1:18 PM    Report this comment

Having a Yamaha outboard, they recommend the regular use of their own brand Ring Free Fuel Additive. I wonder how well that product really works? Although, Yamaha only indicates the additive's usefulness is for preventing the buildup of deposits in the combustion chamber.

Curiously enough, I also have a waverunner from Yamaha and that owners manual mentions nothing about fuel additives (other than a stabilizer at the end of the season). I would believe that the two engines utilize similar technologies.

Pete Serdaru

Posted by: PETER S | February 29, 2012 12:36 PM    Report this comment

When E10 was introduced, it raised hell with the Atomic 4 in the Pearson 30 I owned at the time. Even though I regularly drained suspiciously milky-white liquid and water out of the fuel-water separator and changed its filter, the E10 cleaned all the accumulated material (varnishes, etc.) in the fuel tank and dumped it into the carburetor, totally plugging it and requiring a carb rebuild.

Since I live in MA near the VT border, I started buying regular gas in VT that had no ethanol at all. That worked fine until 2008 when VT introduced E10. After talking with the head of the Fuel Distributors Association in VT, I learned that high test in VT has no ethanol, and switched to that for the Atomic 4 and for all my two cycle engines (outboards, chainsaws, weed wackers, etc.) and since then have never had a fuel problem.

I have been told by other boaters that high test in MA may also not have any ethanol, but haven't been able to confirm that.

Grant Ingle
Padanaram and Conway MA

Posted by: GRANT I | February 29, 2012 10:52 AM    Report this comment

What about bacteriocide addatives and storage addatives? Did you test these?

Posted by: ZVI D | February 29, 2012 10:51 AM    Report this comment

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