gas tank vs petrol tank

gas tank and petrol tank both are nouns.

Word	Noun	Adjective	Verb	Adverb
gas tank	Yes	No	No	No
petrol tank	Yes	No	No	No

As nouns, gas tank and petrol tank are synonyms defined as:

gas tank and petrol tank: a tank for holding gasoline to supply a vehicle

Other synonyms of gas tank include gasoline tank.

gas tank (noun)	petrol tank (noun)
a tank for holding gasoline to supply a vehicle	a tank for holding gasoline to supply a vehicle