Liquefied natural gas
Combustible cryogenic fuels offer much more utility than most inert fuels can. Liquefied natural gas, as with any fuel, will only combust when properly mixed with right amounts of air. As for LNG, the bulk majority of efficiency depends on the methane number, which is the gas equivalent of the octane number. This is determined based on the methane content of the liquefied fuel and any other dissolved gas, and varies as a result of experimental efficiencies. Maximizing efficiency in combustion engines will be a result of determining the proper fuel to air ratio and utilizing the addition other hydrocarbons for added optimal combustion.