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September 29, 2009
Article

What is “phase separation?”

by Eva Murray

According to literature provided to fuel dealers by Irving, "Phase separation occurs when the ethanol blended into the fuel absorbs enough water to separate from the gasoline. It only takes a small amount of water to cause phase separation in a tank, making it critical that ethanol-blended gasoline is not exposed to water at any time. When phase separation has occurred, anywhere from 40 to 80 percent of the ethanol will be pulled out of the gasoline and settle with the water to the bottom of the tank. This ethanol-water mix will not burn...The fuel remaining on top will have a lower octane..."

Ethanol is an oxygenate additive, which helps to reduce toxic emissions such as benzene and carbon monoxide, and does not threaten groundwater as did MTBE, which ethanol replaces. It does offer a lower "energy density" than straight gasoline, however. Some have observed that whatever good comes from reducing the amount of petroleum in each gallon of gas is defeated by the increase in the number of gallons of fuel required to make a trip

Perhaps more worrisome is the dissatisfaction expressed by owners of vintage engines, small engines of many kinds including snowmobiles, yard equipment and chainsaws, marine engines including outboards, and by isolated consumers who have no choice but to store gasoline for extended periods of time, such as islanders. The chemical properties of ethanol are destructive to natural rubber, Neoprene and some similar materials, to fiberglass and certain other composites, to zinc galvanized surfaces, and according to one boatyard mechanic I spoke with, to aluminum. Hoses, gaskets, rings etc. in some engines are susceptible to considerable damage.  Not all "E-10" is exactly 10 percent ethanol, and higher ratios are destructive to some equipment, according to industry literature. A strong solvent, ethanol will dissolve and release all kinds of material, which may be present in fuel tanks and lines to clog or damage fuel system components.

Thanks are due Maine Coast Petroleum, Scott Appleby of Spruce Head Marine and several area mechanics who provided background information for these articles. Information also came from Professional Boatbuilding Magazine (particularly an article by Aaron Porter), the Maine DEP Web site, several proprietary Web sites for fuel testing equipment and outboard motor manufacturers.

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