As used in this chapter, "alternative fuel" means liquefied petroleum gas, a compressed natural gas product, or a combination of liquefied petroleum gas and a compressed natural gas product, not including a biodiesel fuel or biodiesel blend, used in an internal combustion engine or a motor to propel a motor vehicle. The term includes all forms of fuel commonly or commercially known or sold as butane, propane, or compressed natural gas.
IC 4-4-32.2-1