Petroleum prices are making electric vehicles and engines which run on biofuels look more and more attractive with each passing day. That's why its likely to be a hot topic this election season as each presidential candidate sets out his own unique proposals to ease the country into a new era of lower fuel consumption. Biofuels may be the quickest path to lower petroleum usage, but it's electric vehicles which present the biggest step forward in clean auto technology looking forward.

Audi has been quietly going about the business of preparing its lineup for a green future, with cleaner and more efficient diesels in Europe, and oil-burners scheduled for the US in the near future. While the German automaker realizes diesel will be big in the next 10 years, it's also planning for life without emissions. Audi exec Rupert Stadler says the four-ringed automaker is primed to offer an electric vehicle in the next five to ten years.

Click on the image to view high-res shots of the Mercedes F700 concept

Efficiency is a large stumbling block if you're looking for a way to replace gasoline. It's pretty hard to better such an exceptional fuel, and several alternatives show promise but are nagged by inefficiencies or cost, and usually both.