Best practice to protect an engine when not in use that uses any type of alcohol mixed with gas is to shut off the fuel line and run the engine until it runs out of gas. Engine fuel systems with gas and ethanol usually corrode with rust when left sitting. Most fuel treatments sold to remove water from fuel actually are mostly composed of an alcohol type product which makes the situation worse. Check the internet for a lot more information.

Good alcohol is best used for drinking and in stoves.