It's a complex mixture of hydrocarbons, Primarily alkanes, Cycloalkanes, Alkenes, & Aromatics, Along with various additives. These hydrocarbons, Derived from crude oil through distillation, Have properties that make them suitable for combustion in engines.

(For The Periodic Table Element's, You Can Look That Up On Google For Extra Details If You Want Too)

It Is Also ⚠️HIGHLY FLAMMABLE⚠️