[David in San Antonio]

Ethanol is highly hydroscopic , that is, it absorbs water like crazy, even humidity from the air. This can rust the inside of an uncoated Model A fuel tank.
Ethanol does have some upsides. “Dry Gas” is ethanol, which comes in handy if you get some water in the fuel. Adding ethanol allows the water to go through the engine. Another potential benefit of ethanol is that it cools the intake charge, and can boost the anti-knock properties of the fuel, potentially allowing a higher compression ratio.