The heat turns such hydrocarbons into a vapor. If the gasoline contained too many of these hydrocarbons, the resulting vapor could cause vapor lock, an interruption in the flow of gasoline to the engine. Gasolines contain a number of additives. One important group of additives are special oxygen-containing chemicals called oxygenates. These chemicals have high octane numbers and may make up as much as 10 percent of a gasoline.
Gasolines also contain smaller amounts of a number of other additives.
Antioxidants keep the gasoline from becoming gummy. Anti-icers prevent ice from clogging gas lines in winter. Antirust agents prevent tanks and fuel lines from rusting. Detergents and deposit modifiers clean off or prevent engine deposits caused by the burning of gasoline. Metal deactivators keep small amounts of metal impurities from changing the properties of gasoline.