petrol engine vs gasoline engine

petrol engine and gasoline engine both are nouns.

Word	Noun	Adjective	Verb	Adverb
petrol engine	Yes	No	No	No
gasoline engine	Yes	No	No	No

As nouns, petrol engine and gasoline engine are synonyms defined as:

petrol engine and gasoline engine: an internal-combustion engine that burns gasoline; most automobiles are driven by gasoline engines

petrol engine (noun)	gasoline engine (noun)
an internal-combustion engine that burns gasoline; most automobiles are driven by gasoline engines	an internal-combustion engine that burns gasoline; most automobiles are driven by gasoline engines