add fuel to the fire vs cap it all off

add fuel to the fire

verb
  • Used other than figuratively or idiomatically: see add, fuel, fire. 

  • To worsen a conflict between people; to inflame an already tense situation. 

cap it all off

verb
  • To finish or complete something; to add a finishing touch. 

  • To surpass or outdo something. 

How often have the words add fuel to the fire and cap it all off occurred in a corpus of books? (source: Google Ngram Viewer )