Natural gas can only be liquefied under extremely high pressures and very low temperatures. It is also a fairly simple fraction containing mainly propane and butane . Being able to store them as a liquid reduces the container size by a factor of a hundred . This is no doubt why propane stoves are so popular. As cracking methods have evolved more and more LPG has been produced by refineries.
Gasoline is a light fraction of petroleum which is quite volatile and burns rapidly .
Straight run gasoline refers to gasoline produced by distillation instead of cracking, although it really doesn't make a difference. Today, the average American uses 450 gallons of gasoline a year . Octane Number rates a fuel's ability to avoid premature ignition called knock . Premature ignition reduces an engine's power and quickly wares it out . Isooctane is then added to heptane until the mixture has the same knock characteristics as the fuel being tested, and the percent isooctane is taken as the unknown fuels octane number.