The idea of burning multiple types of fuel in a car isn't new—General Motors Company [NYSE:GM] and other carmakers have had flex-fuel vehicles on the road for years now. But doing so efficiently is a whole other challenge. Last December, we brought you word that Lotus had figured out how to make its Omnivore engine up to 10 percent more efficient than a state-of-the-art direct-injection gasoline engine thanks to the use of a two-stroke cycle and a variable compression ratio.

The variable compression ratio works by using a puck in the cylinder head to optimize the fuel burn. The system can go as high as a 40:1 compression ratio. That's a sky-high figure--a typical modern engine lies somewhere between 10:1 and 13:1. But it lets Lotus cram more air in with the fuel to get the most out of every drop, no matter what ratio of alcohol or gasoline that drop's made of.


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