fossil fuel vs petrol

fossil fuel

noun
  • Any fuel derived from hydrocarbon deposits such as coal, petroleum, natural gas and, to some extent, peat; these fuels are non-renewable, and their burning moves carbon from underground into the atmosphere via the greenhouse gas carbon dioxide. 

petrol

noun
  • petroleum, a fluid consisting of a mixture of refined petroleum hydrocarbons, primarily consisting of octane, commonly used as a motor fuel. 

  • A motor vehicle powered by petrol (as opposed to diesel). 

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