Destroyer
God
Got this in my eMail today.. thought it was important enough to repost here. 
From the Boat U.S. Marine Insurance site:
Avoiding the Ethanol Blues
If your boat's engine runs on gasoline, then you need to be careful how you put your fuel to bed for the winter. These days, most gasoline you buy at a gas station or fuel dock comes with 10 percent ethanol, which can cause problems if stored for months, especially if the temperature is changing. Ethanol is hydrophilic - it attracts and holds water. Small amounts of water will be burned in the combustion cycle, but ethanol can only absorb so much water. When it becomes completely saturated, phase separation occurs, and the corrosive ethanol-water mixture sinks to the bottom of the tank. If the engine is run, this mixture can damage seals, O-rings, injectors, and other delicate engine parts. The upper "gasoline" layer will be depleted of ethanol and have a reduced octane level, which can also cause engine problems. Leaving your tank half full for the winter can greatly increase the problems. First, there is more room in the tank and less fuel, which means more surface area for condensation formation and less ethanol to absorb the resulting water. Second, cycling temperatures from warm to cold also increases the amount of condensation. Finally, ethanol cannot absorb as much water at low temperatures as it can when it's warmer, so the gasoline will phase separate more quickly in colder temperatures. So, what should you do? If you can empty your tank completely, you should do so. If not, add stabilizer and fill it most of the way, leaving room for expansion and contraction of the gasoline.
From the Boat U.S. Marine Insurance site:
Avoiding the Ethanol Blues
If your boat's engine runs on gasoline, then you need to be careful how you put your fuel to bed for the winter. These days, most gasoline you buy at a gas station or fuel dock comes with 10 percent ethanol, which can cause problems if stored for months, especially if the temperature is changing. Ethanol is hydrophilic - it attracts and holds water. Small amounts of water will be burned in the combustion cycle, but ethanol can only absorb so much water. When it becomes completely saturated, phase separation occurs, and the corrosive ethanol-water mixture sinks to the bottom of the tank. If the engine is run, this mixture can damage seals, O-rings, injectors, and other delicate engine parts. The upper "gasoline" layer will be depleted of ethanol and have a reduced octane level, which can also cause engine problems. Leaving your tank half full for the winter can greatly increase the problems. First, there is more room in the tank and less fuel, which means more surface area for condensation formation and less ethanol to absorb the resulting water. Second, cycling temperatures from warm to cold also increases the amount of condensation. Finally, ethanol cannot absorb as much water at low temperatures as it can when it's warmer, so the gasoline will phase separate more quickly in colder temperatures. So, what should you do? If you can empty your tank completely, you should do so. If not, add stabilizer and fill it most of the way, leaving room for expansion and contraction of the gasoline.
