The expression "poured oil on troubled waters" means to calm down a difficult situation by taking diplomatic actions. Synonyms for this phrase include "smooth things over," "iron out differences," and "diffuse tension." These phrases describe the act of mediating or finding common ground to mitigate conflicts. Other synonyms include "settle a dispute," "ease tensions," and "restore harmony." To "quell an argument" or "calm a storm" may also be used as substitutes. The use of these phrases emphasizes the need to reduce tension and resolve differences in a non-confrontational and peaceful manner.