Butanes are primarily used as a gasoline blendstock. Butane also plays a minor role in liquefied petroleum gas, refrigerant gas, cigarette lighter fuel, synthetic rubber, and as an aerosol propellant. Butane is colorless and odorless at room temperature. There are 2 forms of butane: Normal butane and isobutane. Normal butane blended with propane forms the automotive fuel, Autogas. Normal butanes high octane rating makes it a great component for gasoline blendstock. However, most refineries turn normal butane into isobutane. Isobutane is then converted into isobutylene for the use in the production of the octane enhancer, MTBE. However, butane demand in the US has gone down recently due to MTBE bans. MTBE readily dissolves in groundwater and transmits a very unpleasant taste. Gasoline blenders have turned to ethanol as an octane enhancer.