Wiktionary
pour oil on troubled waters
vb. (context idiomatic English) To calm something or someone who is tenacious or misbehave.
Usage examples of "pour oil on troubled waters".
It is precisely that we have no bread to throw, said the Bursar, trying to pour oil on troubled waters.
Olivia said quietly, tacitly agreeing to be Victoria, and hoping to pour oil on troubled waters.
You can never tell when he's going to come strolling out of the shadows with a smile and a quip, to pour oil on troubled waters, or occasionally vice versa.