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Living with E-10 Gasoline: The Quest for Truth
By
Matthew A. Cohen
By now, just about every recreational boater and professional fisherman knows
that E-10 gasoline, (10% ethanol) is bad news for them. But just how bad is it,
really? First: the facts. Ethanol is here to stay. It’s a homegrown alternative and
renewable fuel, and as manufacturing plants modernize and become a “closed-
loop system”, meaning the refinery is run on the ethanol they produce, it will
eventually require no imported oil to produce. It is important to our national
energy security, and that’s the fact. So if you own an older boat, (pre-1985) and
it has a fiberglass fuel tank, consider it your donation to the fight against oil
imports, because you probably have to replace it. Ethanol can dissolve many old
fiberglass resins, it will harden into black deposits on your valves, and then you
may blow your engine. Much has already been written on the actual mechanism
of these resin failures in journals such as Boat US, so we won’t address it
technically in this article.
For the rest of you, while E-10 isn’t the best fuel choice for marine use, it isn’t the
end of the world. Here are the facts, along with the Do’s and Don’ts of how to
handle E-10 safely in your boat.
Ethanol is alcohol. Alcohol loves water. It mixes infinitely with water. Once
mixed, they stay mixed. This is because both alcohol and water are “polar”,
which means they have electric charges, in this case, charges that cause
attraction to each other. (Picture the static “cling” that draws dust to your TV
screen). The technical term for something that loves water enough to suck it
right out of the air is “hygroscopic”. You will hear that a lot in conversation if you
talk to either science nerds or fuel additive salespeople.
Gas (and diesel), are pretty much electrically neutral, or “non-polar”. Left to
themselves, they won’t hold much water in suspension. Nor does gas like
ethanol all that much. Small amounts of ethanol can be d