Gasoline or gas (North America) or petrol (Commonwealth countries) is a fuel derived from petroleum, which is in turn generally thought to be derived from ancient vegetable matter. Gasoline is an aliphatic hydrocarbon, or the molecules are composed of nothing but hydrogen and carbon in long chains. The energy contained in a gallon of gasoline is approximately 132x106 joules of energy, equivalent to 120,286 BTU or 35,252 watt-hours. However, Diesel fuel is much more efficient and has an energy density of 139,000 BTU.
Gasoline is refined from crude oil via distillation. Gasoline is sold at gas or fueling stations where it is pumped into vehicles. Gasoline is usually sold in three grades: regular (87 octane in most places, and the cheapest), a mid-level grade (89 octane) and premium (93 octane, usually the most expensive). Some stations also sell a gasoline mix which is 85% gasoline and 15% ethanol which has an 88 octane level (branded as "Unleaded 88" or "E15" and is commonly cheaper than regular gasoline by a few cents).
According to national figures from the U.S. Department of Energy, in May 2007, 46% of the cost of gasoline went to pay for crude oil, 28% for refining, 13% to taxes, and 13% for distribution and marketing. While prices have risen to new highs, in inflationary terms, gas prices are still lower than during the 1973 Energy Crisis or the 1979 Energy Crisis. Prices have gone down since the Trump Presidency.