A complex mixture of naturally occurring hydrocarbon compounds found in rock. Petroleum can range from solid to gas, but the term is generally used to refer to liquid crude oil. The main petroleum products, their usages and their main characteristics are: LPG (heating – pressure, ability to burn as gas); benzene (cars – octane number), naphtha (industry – boiling range), jet fuel (planes – freezing point -47 degrees Celsius), gasoil (trucks – cold characteristics), oil (engine oils – viscosity), diesel (power stations – viscosity), bitumen (roads – stickiness and elasticity)