By the way, the only presidential candidate who has a coherent policy on this is Hillary, but he finds her approach a little too timid. The fastest way to progress is to mandate all cars to have these engines, and then the market will provide the pumps and the multiple possibilities of fuels that compete with oil very well indeed. Hydrogen and plug-in hybrids are more expensive. Biofuels are here now.
His talk on C-Span is here: