The Best Choice of Four-fuels is Fiat Siena Tetra Power
Here is a world first for automotive technology: the four-fuel Fiat Siena developed under Magneti Marelli of Fiat Brazil. Are you a big fan of ethanol as fuel? The Fiat Siena's got you covered. Only pressed, distilled dinosaur on the menu when your automobile tank gets hungry? Pull over and tank 'er up, not a problem for your Fiat Siena. Are you getting "fuel envy" listening to your green friend rave about their recent retrofit to use Compressed Natural Gas? Pull your Siena into the queue, you can run on CNG too. Number four, well, its a bit of a stretch being gasahol--a combination of alcohol and gasoline, fuels 1 + 2. The Siena ELX 1.4 Tetra fuel does another trick too: it is smart enough to choose automatically between the various available fuels, optimizing performance and fuel economy. The system is based on a fully integrated system, and is not a "cheat-by-retrofit to grab some headlines" item. The trick is a unique engine control unit (ECU) system which manages the different types of fuel equally well.
You probably won't see a flood of four-fuel cars in any one market. More likely, automobile manufacturers will embrace the new ECU to optimize production efficiencies, using the same engine technology for a range of models, and varying the fuel supply according to the preference of the market where the car will be sold. Of course, a retrofit to a different fuel will be easier and cheaper for a car equipped with the Marelli ECU because current retrofits require changing a whole series of components in the fuel management system, not just the tank. Fiat Brazil has promised the Siena for the local market by the end of this year. See the Fiat gear-head page Italiaspeed for a good English language write-up on the technology and the debut of the Siena Tetra Fuel at the 8th Michellin Challenge Bibendum in Paris.