leaded gasoline vs petrol

leaded gasoline and petrol both are nouns.

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

As nouns, petrol is a hypernym of leaded gasoline; that is, petrol is a word with a broader meaning than leaded gasoline:

leaded gasoline: gasoline treated with a lead compound to reduce motor knocks
petrol: a volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines

Other hypernyms of leaded gasoline include gas, gasolene, gasoline.

leaded gasoline (noun)	petrol (noun)
gasoline treated with a lead compound to reduce motor knocks	a volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines