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Fuel Stabilizers for Gasoline and Other Information

Because E-10 gasoline has a much shorter "shelf-life" than blended gasoline, Wayne Bauman, Treasurer for the Beaverton Power Squadron, recommends three different products boaters can use with E-10:

Marine Formula Sta-Bil

• Soltron Enzyme Fuel Treatment

• Star Tron Gasoline Additive

These products stabilize the E-10 for up to one year.  They also have a petroleum distillate base instead of an isopropyl alcohol and OMC2+4 Fuel Conditioner that are recommended for regular (non-blended) gasoline.

Background, Precautions and Water Hazards

E10 is increasing in popularity for two main reasons: our nation's fuel demand, and our environmental impact awareness. Ethanol can be produced domestically; it performs as an effective oxygenate, reducing harmful emissions such as benzene. It doesn't contaminate groundwater the way the gasoline additive methyl tertiary butyl ether (MTBE) can.

Boats and Ethanol Gasoline

For the marine industry, though, ethanol raises some issues.  Ethanol is a solvent that doesn't mix well with the additive MTBE fuel in some tanks.  Combining MTBE with E10 scours fuel systems, overburdening filters, breaks down fiberglass fuel tanks and rapidly absorbs water from atmospheric humidity.  The result is a brief shelf life.  Incorporating E10 into fuel is changing the way gasoline-powered boats are maintained, serviced, used and even constructed.

The good news is that there are many ways to protect boats, owners, builders, and repairers from the potential hazards of the switch to ethanol.


Run a non-alcohol fuel stabilizer in your boat's fuel system at all times; especially recommended for engines that sit for a lengthy period of time.

The more use the boat gets, the less likely it is to have problems.

*If you winterize your boat and don't plan on using it for a while, keep your tank 95% FULL to prevent any condensation but allow room for expansion. It's important to avoid water intrusion into your fuel system. (See Water Hazards below for more detail on why.) Here are a few extra tips:

• Install a water-separating fuel filter.

• Keep a stock of spare fuel filters handy, and the means for safely changing them.

• Replace older weather-faded plastic portable tanks with new tanks.

• Make sure you know what your fuel retailer is dispensing.

• Rubber fuel lines older than the mid-to-late 1980s should be inspected and may need to be replaced.

• Some older carbureted engines may require special tuning. Consult the engine manufacturer for details.

Water Hazards

Ethanol absorbs water extremely well. Marine fuel systems are very susceptible to water intrusion. E10 has the ability to absorb a certain amount of water into solution and simply allow it to be burned by the engine.  Here's the comparison: MTBE gasoline can hold about 60 ppm (parts per million) of water in solution; E10 can hold 6,000 to 7,000 ppm of water in solution.  Meaning, if you have a 100 gallon (378.5 liters) tank, it could hold up to .6 - .7 gallons (2.3 - 2.6 liters) of water in solution.

The biggest problem with ethanol for an alternative is with "phase separation." That's what happens when the fuel is saturated beyond it's capacity to hold water in solution.  Water and gasoline actually separate, and the gasoline floats on top of the water.  With MTBE you could simply pump the water out from under the gasoline, or let your filters remove the water.  With E10, ethanol blends more easily with any water.  When phase separation occurs in E10, the ethanol is pulled out of the gas and absorbed by water.  This results in two solutions, neither of which is good for the engine or fuel system...not to mention the environment.  The gasoline left behind is absent of oxygenate. The water left behind now contains a high concentration of ethanol; this solution is highly corrosive and damages any material it may come in contact with in the fuel system. The only solution for phase-separated fuel is to dispose of the entire fuel load, clean the tank, and start over with a fresh tank of E10.

E10's ability to absorb water has yet another drawback; it can absorb water directly from the atmosphere through the vent while simply sitting in the tank.  In just 100 days at 70% humidity, E10 can absorb enough water to phase-separate.  The shelf life of E10 is only 60-90 days if left without treatment.

Another important fact to remember is that gasoline "oxidizes" when exposed to air. That is, it loses its volatility over time.  A good non-alcohol fuel stabilizer is highly recommended at all times in your boat's fuel. *The key is to not leave a boat for long periods of time with a large load of fuel aboard.


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