The component chemicals of petroleum are separated by distillation. Products based on refined crude oil include kerosene, benzene, gasoline, paraffin wax, asphalt, etc.

Strictly speaking, petroleum consists entirely of hydrocarbons, compounds of hydrogen and carbon.

The four lightest alkanes - CH₄ (methane), C₂H₆ (ethane), C₃H₈ (propane) and C₄H₁₀ (butane) - are all gases, boiling at -107°C, -67°C, -43°C, and -18°C, respectively (-161°, -88°, -46°, and -1° degrees F).

The chains in the C_5-7  range are all light, easily vaporized, clear naphthas. They are used as solvents, dry cleaning fluids, and other quick-drying products.  The chains from C₆H₁₄ through C₁₂H₂₆ are blended together and used for gasoline. Kerosene is made up of chains in the C₁₀ to C₁₅  range, followed by diesel fuel/heating oil (C₁₀ to C₂₀) and heavier fuel oils as the ones used in ship engines. These petroleum compounds are all liquid at room temperature.

Lubricating oils and semi-solid greases (including Vaseline®) range from C₁₆ up to C₂₀.
Chains above C₂₀ form solids, starting with paraffin wax, then tar and asphaltic bitumen.
Boiling ranges of petroleum atmospheric pressure distillation fractions in degrees Celsius:
" petrol ether: 40 - 70 °C (used as solvent)
" light petrol: 60 - 100 °C (automobile fuel)
" heavy petrol: 100 - 150 °C (automobile fuel)
" light kerosene: 120 - 150 °C (household solvent and fuel)
" kerosene: 150 - 300 °C (jet engine fuel)
" gas oil: 250 - 350 °C (Diesel fuel/ heating)
" lubrication oil: > 300 °C (engine oil)
" remaining fractions: tar, asphalt, residual fuel