fossil oil vs crude

fossil oil and crude both are nouns.

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

As nouns, fossil oil and crude are synonyms defined as:

Other synonyms of fossil oil include crude oil, oil, petroleum, rock oil.

fossil oil (noun)	crude (noun)
a dark oil consisting mainly of hydrocarbons	a dark oil consisting mainly of hydrocarbons

fossil oil (adjective)	crude (adjective)
	not refined or processed
	belonging to an early stage of technical development; characterized by simplicity and (often) crudeness
	conspicuously and tastelessly indecent
	not processed or subjected to analysis
	devoid of any qualifications or disguise or adornment
	not carefully or expertly made