fuel vs liquefied petroleum gas

fuel

noun
  • Substance consumed to provide energy through combustion, or through chemical or nuclear reaction. 

  • Substance that provides nourishment for a living organism; food. 

  • Something that stimulates, encourages or maintains an action. 

verb
  • To exacerbate, to cause to grow or become greater. 

  • To provide with fuel. 

liquefied petroleum gas

noun
  • A mixture of propane and butane with traces of some other gases, which is kept in a liquid state at high pressure in metal bottles, and used as a source of gas for cooking, heating and as a fuel in internal combustion engines in vehicles. 

How often have the words fuel and liquefied petroleum gas occurred in a corpus of books? (source: Google Ngram Viewer )