With the ink still wet on a congressional mandate to boost fuel economy to 35 mpg by 2020, every auto maker at this year's Detroit auto show is talking about fuel consumption — even Ferrari SpA.

The Italian icon for exotic sports cars unveils a concept F430 Spider Biofuel designed to run on E85, an alternative fuel made up of 85% ethanol and 15% gasoline.

A growing number of E85 flex-fuel vehicles now are now available in the U.S., particularly fullsize pickups and SUVs.

But the F430 Spider Biofuel is purely a concept, and there are no immediate plans for production, says Amedeo Felisa, Ferrari general manager.

“We show it in Detroit because there is a natural interest in biofuels,” Felisa tells Ward's. “If the reaction is positive, then we will be ready with the next model to install the solution.”