Binary, hexadecimal, and octal refer to different number systems. The one that we typically use is called decimal. These number systems refer to the number of symbols used to represent numbers. In the decimal system, we use ten different symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. With these ten symbols, we can represent any quantity.
We have two majors: a Bachelor of Science in geology and a Bachelor of Arts in geoscience. The B.S. in geology is a rigorous and well-rounded geology major that teaches all of the general skills needed to be successful for employment or graduate school in the field of geology.
If you want to do petroleum engineering, major in petroleum engineering. There is no need for a geology degree if you want to do engineering. Mechanical engineering is the jack of all trades, master of none discipline. It can be used for many fields, including petroleum engineering. If you don't want to major in petroleum engineering, chemical engineering is probably closer than mechanical for what you want to do.