Most gas line antifreeze is made up of mostly isopropyl or methyl alcohol. Alcohol has a very low freezing point, which makes it especially useful for this. However, it is important to recognize that most fuel sold in the United States already has ethanol alcohol blended with the fuel. Ethanol is blended in a mixture between 5 and 20 percent of most fuel. This means that adding additional gas line antifreeze could be an unneeded measure if your vehicle is generally operating in environments that are not extreme. [links]