Petroleum is used mostly, by volume, for refining into fuel oil and gasoline, both important primary energy sources. 84% by volume of the hydrocarbons present in petroleum is converted into fuels, including gasoline, diesel, jet, heating, and other fuel oils, and liquefied petroleum gas.
Due to its high energy density, easy transportability and relative abundance, oil has become the worlds most important source of energy since the mid-1950s. Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics; the 16 percent not used for energy production is converted into these other materials. Petroleum is found in porous rock formations in the upper strata of some areas of the Earths crust. There is also petroleum in oil sands (tar sands). Known oil reserves are typically estimated at 190 km (1.2 trillion (short scale) barrels) without oil sands, or 595 km (3.74 trillion barrels) with oil sands. Consumption is currently around  per day, or 4.9 km per year, yielding a remaining oil supply of only about 120 years, if current demand remains static. More recent studies, however, put the number at around 50 years.
Closely related to fuels for combustion engines are Lubricants, greases, and viscosity stabilizers.  All are derived from petroleum.