Liquid methane
Liquid methane is the presently ubiquitous fuel source for most automobiles in the system. This is chiefly as a result of the technological advancements that were achieved in the isolation and stabilization of liquid methane, as it was seen as a promising alternative to traditional fossil fuels such as oil and coal. A cleaner-burning fuel, it produces less carbon dioxide and fewer toxic chemicals such as nitrogen oxides and sulfur dioxide, while simultaneously having greater cost effectiveness through higher energy density compared to gasoline. Apason, a nearby planet whose atmosphere is inundated by the presence of methane, has become the primary source of such fuel for the three political blocs of Plateia. Large interplanetary transport networks have developed to exploit such a fount of fuel, stretching from Apason to Plateia and even to other regions that utilize automobiles, such as Vasati.
Liquid methane is always kept at extremely low temperatures, within environmentally isolated tanks that prevent heat transfer and subsequent vaporization. With carburetors engineered specifically for use within such a system, liquid methane is then directed towards engines that have been attuned for such use: this mainly includes traditional spark-ignition engines, but can include high-pressure direct-injection engines that simultaneously use diesel for higher energy efficiency (versus traditional stoichiometric gas engines).
Refueling liquid methane for automobiles has been conventionalized to that of liquid methane refueling stations akin to the gasoline stations of old, or the alternative electric vehicles of the present. However, due to its extremely high flammability, it poses greater risks when leaking from a tank or other infrastructure carrying the methane.