Oil is found in the Earth's crust, which is the outermost layer of the Earth.

Here's a breakdown:

* Crust: This is the solid, rocky layer we live on. It's relatively thin compared to the other layers.

* Mantle: This is a thick layer of hot, dense rock beneath the crust. Oil isn't found here.

* Core: The Earth's core is made up of a solid inner core and a liquid outer core. Oil isn't found here either.

Oil forms over millions of years from the remains of ancient marine organisms buried under layers of sediment. This process happens within the Earth's crust, specifically in sedimentary rock formations.