What chemicals are used as additives in gas today?

Gasoline is generally viewed in regards to its octane value. In reality, there is very little octane in gasoline. There is actually a great deal of hexane. Additives vary, but are generally other organic compounds of the cyclic variety, benzene and toluene among them. It's a mive mixture of hundreds, if not thousands of chemicals which are blended for performance, pollution control, etc.