residual oil vs crude oil

residual oil and crude oil both are nouns.

Word	Noun	Adjective	Verb	Adverb
residual oil	Yes	No	No	No
crude oil	Yes	No	No	No

As nouns, crude oil is a hypernym of residual oil; that is, crude oil is a word with a broader meaning than residual oil:

Other hypernyms of residual oil include crude, fossil oil, oil, petroleum, rock oil.

residual oil (noun)	crude oil (noun)
oil products that remain after petroleum has been distilled	a dark oil consisting mainly of hydrocarbons