oil heater vs oilstove

oil heater and oilstove both are nouns.

Word	Noun	Adjective	Verb	Adverb
oil heater	Yes	No	No	No
oilstove	Yes	No	No	No

As nouns, oil heater and oilstove are synonyms defined as:

oil heater and oilstove: heater that burns oil (as kerosine) for heating or cooking

Other synonyms of oil heater include kerosene heater, kerosine heater.

oil heater (noun)	oilstove (noun)
heater that burns oil (as kerosine) for heating or cooking	heater that burns oil (as kerosine) for heating or cooking