petrol vs vegetable oil

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). 

vegetable oil

noun
  • Any oil produced from plants, such as olive oil and corn oil, mostly used for cooking. 

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