fuel-saving vs prudent

fuel-saving

prudent

adj
  • Frugal, economical. 

  • Sagacious in adapting means to ends; circumspect in action, or in determining any line of conduct. 

  • Practically wise, judicious, shrewd. 

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