car factory vs auto factory

car factory and auto factory both are nouns.

Word	Noun	Adjective	Verb	Adverb
car factory	Yes	No	No	No
auto factory	Yes	No	No	No

As nouns, car factory and auto factory are synonyms defined as:

car factory and auto factory: a factory where automobiles are manufactured

Other synonyms of car factory include automobile factory.

car factory (noun)	auto factory (noun)
a factory where automobiles are manufactured	a factory where automobiles are manufactured