What element are in octane?
What most people mean when they talk about "octane" is slightly different from what a chemist means by the word (a layman's "octane" is a chemist's "isooctane", or 2,2,4-trimethylpentane). However, both octane and 2,2,4-trimethylpentane are hydrocarbons, meaning they contain exactly two elements: hydrogen and carbon.