elbow grease vs effort

elbow grease and effort both are nouns.

Word	Noun	Adjective	Verb	Adverb
elbow grease	Yes	No	No	No
effort	Yes	No	No	No

As nouns, elbow grease and effort are synonyms defined as:

Other synonyms of elbow grease include exertion, sweat, travail.

elbow grease (noun)	effort (noun)
use of physical or mental energy; hard work	earnest and conscientious activity intended to do or accomplish something
	use of physical or mental energy; hard work
	a notable achievement
	a series of actions advancing a principle or tending toward a particular end