When alcohol was tried as a fuel additive in the 1970s the problem was it would eat the plastic and seals in the carburetors. It was the worst in Ford cars.

They also found high concentrations of alcohol would draw moisture out of the air and separate from the gasoline.
The alcohol also tended to rust steel parts like steel fuel lines instead of protecting them like gasoline or diesel fuel does.

Yet straight alcohol was used as a motor fuel before gasoline was and Henry Ford designed his first Model T cars to run on it.
The early John Deer tractors were like that too.

When you buy fuel line de-icer it is usually methanol.