I do not know where you are in the world but in the homeland of the English language, Britain and most of its direct (former!) colonies, "petrol" is the stuff cars and motorbikes run on and "diesel" is the stuff agricultural vehicles and heavy plant (lorries, buses) runs on. "Gas" is a phase of matter along with "liquid", "solid", and "plasma" and that is all the bare noun means. "Natural gas", and the obsolete "coal gas"/"town gas", are fuels, but for heating/cooking/light not vehicles as a rule, but generally we'd talk about propane, butane, etc.
We never, ever use "gasoline" or the Germanic "benzene" for this. Benzene is a specific chemical here, never ever a fuel.
