autogas vs mogas

autogas

noun
  • Automotive gasoline suitable for use in piston-engined gasoline-powered aircraft. 

  • Liquefied Petroleum Gas (LPG) 

mogas

noun
  • Automotive gasoline suitable for use in some piston-engined gasoline powered aircraft. 

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