diesel vs liquefied petroleum gas

diesel

noun
  • A fuel derived from petroleum (or other oils) but heavier than gasoline/petrol. Used to power diesel engines which burn this fuel using the heat produced when air is compressed. 

  • Synonym of snakebite and black. 

  • A rider who has an even energy output, without bursts of speed. 

  • A particular cannabis hybrid. 

  • A vehicle powered by a diesel engine. 

verb
  • To ignite a substance by using the heat generated by compression. 

  • For a spark-ignition internal combustion engine to continue running after the electrical current to the spark plugs has been turned off. This occurs when there's enough heat in the combustion chamber to ignite the air and fuel mixture without a spark, the same way that heat and pressure cause ignition in a diesel engine. 

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 diesel and liquefied petroleum gas occurred in a corpus of books? (source: Google Ngram Viewer )