- You may be looking for petrol, also known as gas.
Gas was a state of matter.
Earth at an early stage of its development was an enormous mass of superhot gases surrounding a core of molten rock. Over millions of years, the sun "eroded away" the gases, causing the planet to solidify. (AUDIO: Exploration Earth)
The Gelth were made of gas. When a human body decomposed, they produced gas. According to the Ninth Doctor, the Gelth could "slip inside [the body and] use it as a vehicle, just like [Charles Dickens'] driver and his coach". (TV: The Unquiet Dead)